1
The ticking of the clock sounded impossibly loud.
It was already after six in the morning... Yuma checked his watch and stole a glance at the couch. Tsukiyo was lying on the three-seater with her hands folded over her abdomen, eyes closed and looking supremely comfortable.
A few hours ago, Tsukiyo had theatrically issued her Challenge to the Reader, after which Yuma and Kuruma had pressed her to identify the culprit, but she had just smiled and said:
“No. Before we can solve the mystery, we need to gather everyone together. Modern mystery novels love to mock the idea of the summation, but solving the case in front of everyone involved is the high point of any great detective's life. I'm not giving that up. So... About 6:30 tomorrow morning should be good. Oh, don't worry, nobody will be killed tonight. Well, I'm going to go recharge until then.”
Yuma and Kuruma begged Tsukiyo to at least tell them who did it, but Tsukiyo stubbornly refused. They had no choice but to give up and leave the First room, Kuruma returning to the game room and Yuma and Tsukiyo returning to the Fourth room.
As soon as they entered the room, Tsukiyo said “Wake me up around six” and lay down. For the next few hours, Yuma sat in bed, waiting for the time to pass, feeling restless and wondering what would happen next.
“Ms. Aoi, wake up. It's six o'clock.”
When he called out, Tsukiyo replied “I'm awake” without opening her eyes.
“How long have you been up?”
“To be honest, I could hardly sleep. I'm as excited as an elementary schooler the night before a field trip. But the real game starts now, so I thought I should at least lie down and rest my body.”
Opening her eyes, Tsukiyo jumped up, tied the tie she'd left hanging on the back of the couch, and put on her suit jacket.
“Well then, Watson, let's gather everyone and put on a show.”
As Tsukiyo made for the door in high spirits, Yuma called out
“Wait.”
“What is it, Yuma?”
“How exactly do you plan to gather everyone? Three people are in the game room, but Mr. Kagami and Ms. Yumeyomi have declared that they won't leave their rooms until the police arrive.”
“That's easy. Listen to me, Yuma, this is how we'll do it.”
Tsukiyo narrowed her eyes and gave Yuma some instructions. When he heard them, Yuma put a hand on the side of his head.
“We're really going to do that?”
“Yes. I need to get some things ready on the first floor, so you go call the two of them. Alright, let's go!”
“Oh, I need to use the bathroom first.”
“Oh, really? Well, I'll go on ahead, then. I'd like to start at 6:30 if possible, so don't linger.”
Yuma saw Tsukiyo off with a wave and went to the bathroom. He went inside and locked the door, then looked into the bathroom mirror. His eyes met the other man's, looking frightened.
“It's okay... I can do this.”
The man in the mirror told him as he pulled out a brown pill case from his jacket pocket.
The great detective would manage to identify the culprit behind the murders of Oita and Madoka. This was his chance. If he could force that pill case on the culprit, he could make them take all the blame for Kozushima's murder.
A tremor arose from deep within his body. Yuma grit his teeth, biting down the tremors, and slapped his hands to his cheeks. A sound like the popping of a balloon and a sharp pain in his face drowned out his doubts.
He had to do this. For his sister's sake.
Yuma confirmed the look of determination on the man in the mirror and left the bathroom.
Yuma left the Fourth room, locked the door behind him, and climbed the stairs to the Second room. He took a deep breath and pounded a fist on the door.
“Mr. Kagami, please come out!”
There was no response. Yuma refused to give up and kept banging on the door.
“What is it!? Shut up!”
After tens of seconds, Kagami couldn't take it any more and sent his rough, ragged voice through the door.
“Could you please come down to the first floor?”
“What are you babbling about? I told you yesterday, I'm not leaving this room until the police get here.”
“The police just arrived.”
Yuma felt his nerves as he repeated the line Tsukiyo had instructed him to say.
“The police are here?”
“Yes, that's right. It looks like the snow clearing finished earlier than expected. For now, everyone is gathering on the first floor.”
Worried he'd be seen through, Yuma waited for a response. He heard the sound of the lock being undone, and the door opened.
“So they're finally here. Seriously, keepin' me waiting...”
Kagami came out wearing a wrinkled shirt, scratching his messy bedhead. Relief washing over him, Yuma followed him down the stairs to the Seventh room, where he told Yumeyomi the police had arrived, just like Kagami. Between her greater paranoia and making him wait while she changed, it took fifteen minutes, but he managed to get Yumeyomi out of her room.
“Where are the police!?”
As soon as she arrived on the first floor, Yumeyomi ran down the hall, her pink dress fluttering in the air, searching for the authorities.
“This way. Please, come to the dining room.”
Hearing Yuma, Kagami frowned and asked
“The dining room? Why the dining room? It's all wet in there.”
“It's been two days, it's dried. Please, come in.”
Yuma spoke quickly and opened the door before they could ask any more questions. Kagami and Yumeyomi hesitantly followed him.
The moment they entered the room, an inappropriately cheerful voice rang out.
“Welcome! Thank you all so much for coming!”
Tsukiyo spread out her arms. Behind her, Kuruma, Sakyo, and Sakaizumi stood, looking as confused as anyone. All the curtains were closed, and the room was lit by the chandelier handing from the ceiling. The carpet on the floor was still wet, but it seemed most of it had evaporated, as she could walk without making squelching noises.
On the table, the words SPIRITED AWAY FROM CHOGATAKE were still written and the burned section was still visible. Also on the table were what appeared to be a film projector, a folded towel, a magic marker, and, for some reason, a watering can full of water. Next to Tsukiyo was the model of the Glass Tower that had been in the game room.
“What's going on here!? You people aren't police officers!”
Yumeyomi screamed, and Tsukiyo bowed.
“Oh, that was a lie to bring you two here.”
Yumeyomi's eyes grew so wide they looked like they'd be forced from their sockets, and she glared at Yuma, asking
“What are you planning?”
“Oh, don't blame Yuma. I told him to say it.”
“What are you all thinking? What is the purpose of this ridiculous act?”
Undeterred by her murderous gaze, Tsukiyo ran a hand through her short hair.
“Of course, as a great detective, I'm going to expose the truth of the case.”
“What!? You mean you know who the culprit is!?”
Yumeyomi's voice cracked. Tsukiyo gave a hearty nod and said “Of course.” A look of slight expectation appeared on the faces of all the men... except Kagami.
“This is stupid. I'm leaving. Don't talk to me again.”
Kagami turned on his heel.
“Hey, wait, where are you going, Mr. Kagami?”
“Back to my room, obviously. I'm not participating in a little girl's make-believe games. When the police get here, they'll tell us who the culprit is. Until then, I'm stayin' in my room.”
Kagami made for the stairs. Yumeyomi seemed to hesitate for a moment, then went to follow him.
“Running away, detective?”
Kagami stopped in his tracks at Tsukiyo's words.
“What was that?”
Kagami turned around slowly, his words low and slow.
“I'm asking if you're afraid. Afraid this 'little girl' is about to expose the truth behind a case that you, a detective from the Prefectural Police's First Investigation Division, were completely stumped by.”
Tsukiyo spoke provocatively, a bewitching smile on her lips.
“Don't underestimate me. There's no way-”
“Then why not listen to my theory? It won't cost you anything. It's the perfect way to kill time until the police arrive.”
“...You might be the culprit, and you're trying to lure us out of our rooms so you can kill us.”
“I see, so the detective is the culprit. How interesting. But there have already been many mystery novels that used that trick, so unless it's executed extremely well, it won't actually come as a surprise anymore. The first thing to come to mind is C-”
“Oh, come on! How many times do I have to tell you, this isn't a mystery novel!”
“You don't know that. Maybe you just haven't realized. Well, setting aside the meta discussions for now, even if I was the culprit, do you really think a weak and fragile woman like me could defeat a police detective? If you're really so unsure of your strength, there's nothing I can do. Lock yourself back in your room and tremble like a frightened fawn. Or...”
Tsukiyo paused, glared right at him, and licked her lips.
“Maybe you're afraid that I'll expose you as the culprit? Is there something you have to hide, detective?”
Kagami finally ran out of patience and strode back into the dining room, both hands in his pockets.
“Even if you say all that, what if your deduction turns out to be wrong? If you accuse the wrong person, how will you take responsibility for that?”
“...If that happens, I'll never call myself a great detective again.”
Her tone was so dark silence fell over the room. Kagami was taken aback for a moment, then pointed at Tsukiyo.
“Not calling yourself a great detective, that's nothing.”
“To me, it's everything,” Tsukiyo replied, firmly locking eyes with him. “I've spent my whole living striving towards the title of 'great detective'. I'd rather be torn in two than give it up. But I swear, I will never work as a great detective again. If I make a false accusation here today, I will never show my face in public again, and live the rest of my life in silence and shadow. That is how seriously I take this case. So please, listen to my theory.”
Kagami didn't argue with Tsukiyo any further after hearing the resolve behind her words. Yumeyomi shrugged and returned as well.
Tsukiyo said “Now then” and clapped her hands at chest height. A satisfying bang echoed through the dining room.
“Now that everyone is here, it's time for the grand finale. I will now tell everyone the truth behind the tragedy that has taken place in this spire of glass, The Glass House Murders.”
Tsukiyo proudly puffed out her chest and declared the beginning of the final chapter.
“So, who is the culprit? Tell us!”
Tsukiyo held out a hand to Yumeyomi, who was leaning forward like she was about to pounce.
“Calm down please. I can't just name the culprit out of nowhere. There is an order to these sorts of things.”
“What are you talking about? Stop messing around and tell us who did this!”
Having been living in fear for dozens of hours straight and long since passed her limit, Yumeyomi tore at her hair with both hands.
“I am not messing around.”
Tsukiyo's voice dropped low. Yumeyomi's hands froze as she looked at Tsukiyo with fear.
“There's a reason detectives in mystery novels explain their conclusions in steps. If I were to just tell you who the culprit is now, without explaining how I realized the truth, no one would find that convincing. It would only cause confusion. I can't just make an accusation. That would give the real culprit a chance to escape... or commit a massacre.”
“Massacre...?”
“Why are you so surprised? The person I'm about to expose is a heinous criminal who's killed three people, left writing in blood at their scenes, and even committed human torture. If they thought I knew they were the culprit, it's only natural that they would try to escape, even if it meant killing everyone here.”
Tsukiyo looked straight at Yumeyomi.
“If they're arrested, they'll surely get the death sentence. So it doesn't really matter how many more people they kill.”
When Yumeyomi wrapped her arms around herself and began to tremble, Tsukiyo suddenly gave a gentle smile.
“So I'll explain everything step-by-step, so everyone understands. Is that okay?”
Seeing Yumeyomi repeatedly nod her head, Tsukiyo raised her index finger next to her face.
“Well then, let's begin. First is the first case in the First room, when Kozushima Tarou was poisoned to death. From Mr. Oita's testimony, we can assume that the poison used was powdered pufferfish liver taken from the Kozushima Collection. The door to the First room was locked, and the glass was fixed and didn't open. In other words, Mr. Kozushima was killed in a locked room. The reason the murderer locked the door is simple: to make it look like Mr. Kozushima died of an illness or committed suicide.”
Everyone in the dining room waited with baited breath for Tsukiyo's answer.
“So, how did the culprit create the locked room? There are only two keys that can lock the door to the First room: the First key and the master key. After inquiring with the company that made the keys, we confirmed that there are no others. The master key was kept in the key cabinet by the fireplace in the game room, which I stood near the whole time, so I can personally confirm that nobody opened it from after dinner on the first day to when we all went to the First room. The theory that Mr. Sakaizumi had the master key from the beginning and only pretended to retrieve it can be refuted by his alibi. After dinner, Mr. Sakaizumi went straight behind the bar and made cocktails for everyone.”
As Tsukiyo recited the facts, Kuruma raised his hand. Tsukiyo looked at him and nodded.
“Sorry to interrupt, but...”
“No, not at all. Every good summation features characters posing questions to the great detective and identifying contradictions in their reasoning. By answering their questions, the shape of the case gradually becomes clear.”
Tsukiyo sounded like she was having the time of her life.
“Well then, I'll be blunt. Since poisoning as a murder method can be set in advance and taken well after the culprit has left, I don't see the point in discussing how the locked room was created. As we've discussed before, if it was poison, it could have been placed in something Kozushima would have ingested ahead of time. The culprit didn't need to be present when Kozushima was poisoned. I believe it's just a coincidence that Kozushima locked the door before swallowing the poison.”
“In that case, it would have been difficult for the culprit to predict exactly when Mr. Kozushima would die. I doubt that it's a coincidence he died right before making an important announcement. In that case, isn't it more likely that the culprit was there at the scene?”
“That was my initial thought as well. But now we know that the culprit's motive was revenge for those who died in the dungeon, and is totally unrelated to Kozushima's announcement that he'd discovered a valuable unpublished mystery novel.”
As expected of one of the greatest mystery novelists of the age, Kuruma was sharp. Tsukiyo listened to him, smiling and occasionally nodding.
“To begin with, the fact that Kozushima had enough time to leave that dying message after taking the poison would mean that, even if the culprit was in the room at the time of the crime, they must have left. That means Kozushima had time to lock the room from the inside to stop them from returning to finish him off. The evidence suggests that the premise that the culprit intentionally created a locked room is wrong, don't you think?”
After asking the question, Kuruma looked to Tsukiyo, face tensed.
“As expected from Mr. Kuruma, a wonderful objection,” Tsukiyo said excitedly. “Your question is appropriate and your concern is logical. It's true that with the information you all have, it can't be determined whether or not the door was locked intentionally by the culprit or if the existence of the locked room was a coincidence. So, Yuma.”
Yuma blinked when she called his name out of nowhere. “Huh?”
“Don't 'Huh?' me. You're my assistant, you need to support me. Don't go spacing out. For now, can you turn off the lights and shut the door?”
Yuma replied “Ah, yes,” and hurriedly did as he was asked. The chandelier was turned off, and the room was cast into darkness. With the faint light filtering in through the gap in the blackout curtains, he could barely make out the outlines of the furniture.
“Now, take a look at this.”
On Tsukiyo's signal, an image of a blue mansion was projected onto the white wall of the dining room.
“I borrowed it from the theater. This wall makes an excellent screen.”
Tsukiyo took her smartphone out of her pocket and started tapping the screen. The image of the blue mansion was replaced by a key on a black floor. The key was engraved “First”.
“This is the key found on the floor of the first crime scene.”
“Hey, wait a minute. When did you take this picture?”
Kagami interrupted her. Yuma started to explain “Actually-”, but Tsukiyo cut him off.
“It was when we all entered the room on the first night. You wouldn't let me take pictures of the body, so I had no choice but to photograph the other evidence.”
In actuality, she had taken it last night. But if she said that, Kagami would yell at her again. Besides, if Yumeyomi found out that the master key had been removed from the safe again, she would probably have another episode.
Yuma looked at Kuruma, who knew the truth. He must have understood their intentions, as he nodded slightly.
“Last night, I was going over the crime scene evidence again and I noticed something very important. Please, take a look.”
When Tsukiyo touched the screen of her smartphone, a video began to play. Thin white fingers picked up the key.
“Wait, you touched the evidence? If you got fingerprints on it-”
“Please be quiet, this is important.”
Kagami was about to complain, but Tsukiyo scolded him and he fell silent, scowling.
The video zoomed in on the carpet and stopped in a close-up.
“Do you understand?”
When Tsukiyo asked, everyone exchanged looks with each other. Perhaps dissatisfied with their reactions, Tsukiyo pursed her lips, approached the wall, and pointed at the video, saying “It's right there, look.”
“I see some sort of white dust...”
Sakyo spoke timidly, and Tsukiyo pointed at him.
“That's right. The carpet you see on the screen is covered in tiny particles.”
“So? What's that supposed to mean, other than that the maid was lousy at her job?”
Kagami shook his head.
“No, that isn't it. Ms. Tomoe and Mr. Oita were both excellent servants. There's no way they would have neglected to clean the room of their employer, Mr. Kozushima. And look closely. Even if it isn't that noticeable, don't you find the fact that this white powder exists at all strange?”
“Alright then, tell us, already. What exactly is that white powder?”
Tsukiyo slapped the wall on which the image was being projected and loudly announced:
“Ash. Cigarette ash.”
“Ash? You mean when Madoka spilled it...”
Perhaps he still hadn't recovered from the shock of losing the woman he loved, or maybe he was hungover, but Sakaizumi's facial muscles were completely limp as he spoke. Tsukiyo turned to him.
“Yes, that's right. When Ms. Tomoe went to call emergency services, she knocked the ashtray off the table. Cigarette ash is quite fine, so it spread over a great distance.”
“So what!?”
Yumeyomi screamed, sounding ready to bite someone's head off.
“You think ashes can tell us anything!?”
“Tell us anything?” Tsukiyo blinked rapidly. “You mean you still don't know? The ashes scattered when Ms. Tomoe knocked over the ashtray were underneath the First key. Not on top of, but underneath.”
“You don't mean...”
Kuruma's eyes went wide.
“So the key fell on the floor...”
“Yes, after Ms. Tomoe dropped the ashtray.”
Yuma's heart skipped a beat. There had been ashes on the floor. Why hadn't he checked where he was dropping the key? He'd seen Madoka knock over the ashtray. Stupid, stupid, stupid...
“Wait, what are you all talking about? I don't understand.”
Yumeyomi was clutching her head as though she had a headache. Tsukiyo gave a dramatic sigh.
“If the key had been there on the floor, the ashes would have landed on top of it. But what we actually have is ashes underneath the key. In other words, this key wasn't placed on the floor until after Ms. Tomoe knocked over the ashtray.”
“Who put it there? And why would they do that!?”
“It was the culprit, of course. They wanted to make the crime scene a locked room to make it look like Mr. Kozushima had died of illness or suicide. After poisoning Mr. Kozushima, the culprit took the First key, left the room, and locked the door from the outside. Then, after we used the master key to unlock the door and enter the room, they quietly left the key on the floor so that it would look like it had been there from the beginning.”
Everyone was absorbed in Tsukiyo's story and remained silent.
“But something unexpected happened to the culprit. Mr. Kozushima picked up the phone and called for help. They managed to wrestle the receiver from him and kept him from telling us who did it, but Mr. Oita became concerned and said he would be there right away. So the culprit fled the room and locked the door behind them without having time to confirm that Mr. Kozushima was dead. That's why Mr. Kozushima was able to leave a dying message.”
“Wait a second,” Kuruma interrupted. “I agree that in the time between dinner and Kozushima's murder, someone must have gone to the First room with poison and left with the First key. But it isn't necessarily true that when Kozushima took the poison and began to suffer the culprit was in the First room. Maybe they put the poison in his drink, then stealthily took the First key, left the room, and locked the door from the outside.”
“No, that isn't the case. Mr. Oita said so, didn't he? Mr. Kozushima always made sure to lock his room. If the culprit had planted poison, stolen the key, and locked the room from the outside, Mr. Kozushima would have immediately noticed that his key had been stolen. Because after the visitor left, Mr. Kozushima would have reached for it to lock the door right away.”
“So if the door had already been locked, he would have immediately known that his visitor stole the key?”
“That's right,” Tsukiyo replied with a smile.
“Um, may I say something?”
It was Sakyo who asked.
“So when Mr. Kozushima called Mr. Oita on the internal line, the culprit was still in the First room? But I remember us all going up the stairs as a group afterwards.”
“Are you sure about that? When Mr. Oita shouted 'It seems something has happened to the master!', we were all doing our own things separately in the game room, which is spacious and full of blind spots due to the number of pillars inside. The only people we can be absolutely sure were there were Mr. Sakaizumi, who was making cocktails behind the bar, and Mr. Oita and Ms. Tomoe, who were serving them.”
“I was in the game room!”
Yumeyomi's hand shot straight up.
“Can anyone prove that?”
“Yes, of course. Look, one of you saw me in the game room, right?”
Yumeyomi looked around, but everyone silently averted their eyes.
“It was a pretty chaotic situation at the time, so everyone's memories must be a blur. In that situation, it's only natural that nobody would have a clear alibi.”
“So someone here really poisoned Mr. Kozushima?”
Sakyo spoke in a rasping voice, and Yumeyomi began wildly scratching her hair.
“No, there's someone hiding in this Tower. I've been saying so all along. There's something dangerous here. Yes, the person who escaped from the dungeon. They're the one who killed Mr. Kozushima.”
“That can't be true, Ms. Yumeyomi,” Tsukiyo admonished. “Looking at the situation, the culprit poisoned Mr. Kozushima in the First room without alerting him. If someone who'd escaped from the dungeon and had been living in the Tower in secret for over a year had entered the room, Mr. Kozushima would have immediately called for help. In the first place, it's impossible for a suspicious outsider to break into the First room, which is always kept locked. The culprit must be someone close enough that Mr. Kozushima would have let them into the room without being on high alert. In other words, someone here. Do we all agree?”
Yumeyomi was shaking with emotion, but she fell silent. It was Sakyo who spoke.
“But after Mr. Oita received the call from Mr. Kozushima, we went to the First room relatively quickly. If the culprit had fled in a panic after the poisoning, wouldn't they have passed us on the stairs?”
“You're right,” Tsukiyo said, excited. “But in reality, we made it to the first room without seeing anyone, and we were all together before we opened the door with the master key and discovered Mr. Kozushima's body. The culprit must have heard Mr. Oita answer the internal line and say he would be there right away, then hurried down the stairs. But we came up before they reached the first floor. So, how did the culprit avoid bumping into us and join us without being seen? There are two possibilities.”
Tsukiyo held up two fingers in a peace sign.
“One is to hide in the display room. There are many blind spots in the display room, so even if we had gone up and checked, they would have had places to hide. It's the perfect hiding place.”
“So the culprit hid in the display room and secretly joined us after we entered the First room?”
“No, that's not true. There's a major flaw with that theory.”
“A major flaw?” Sakyo asked.
“Yes. The door to the display room is extremely heavy, probably because it was made especially sturdy to protect the valuable Kozushima Collection stored inside. As a result, it makes an extremely loud noise when opened, a sound which reverberates all the way down the spiral staircase. If someone had opened the door to the display room, we would have noticed. The culprit actually used another method.”
Tsukiyo lowered her middle finger, leaving only her index finger.
“The culprit, who almost ran into us on their way down the stairs, quickly hid in their own room. Then, after making sure we'd all passed, they came out and joined us, pretending they'd come up from the first floor with the rest of us.”
Tsukiyo stopped with a snap of her fingers.
“This is the truth of the first incident.”
“So... do you know who the culprit is?”
Sakaizumi's voice resonated out from deep within him. His eyes were bloodshot, and two fists trembled at his sides. His whole body was overflowing with rage at the culprit who had taken Madoka from him.
Yuma took a small step away from Sakaizumi. His heart was pounding against his ribs.
Did Tsukiyo know he'd killed Kozushima? Was she going to name him as the culprit and let him be framed for the other two murders?
He was so nervous he was hyperventilating. He couldn't keep air in his lungs no matter how hard he tried. Desperately straining not to collapse on the spot, Yuma waited to hear Tsukiyo's answer.
“Just knowing the truth of the first incident doesn't tell us who the culprit is. It only tells us who it isn't.”
“...Who the culprit isn't?”
Sakaizumi's eyes glared unblinking at Tsukiyo.
“Yes, that's right. As I said before, you, who were making cocktails at the bar, and Ms. Tomoe and Mr. Oita, who were serving them, can all be said to have alibis for Mr. Kozushima's murder. In other words, there are six suspects left.”
Tsukiyo checked her watch.
“Including myself, of course.”
“So, how do we find out who killed Madoka?”
“If we solve the remaining two locked room murders, the identity of the culprit will reveal itself. So, since it's about time, let's move on to the second incident, the brutal murder of Mr. Oita here in the dining room.”
Kuruma cocked his head to the side.
“It's about time?”
“You'll understand soon enough. Now, the primary mysteries of the second incident are how the culprit locked the room, and how they set a fire in the locked room. Those two points. There's also the secondary mystery of why they left their bloody message on the tablecloth, the thing most likely to be burned away, even though they probably did want us to see the message 'SPIRITED AWAY FROM CHOGATAKE'.”
“Have you found the answer to those mysteries?”
Kuruma asked, and Tsukiyo shook her head.
“To be precise, they aren't separate mysteries. The three mysteries I just described are deeply intertwined, and ultimately represent a single phenomenon.”
As Yuma stood confused by Tsukiyo's Zen riddle, she approached him.
“Well, to begin with, it's a locked room. The locked room is the platonic ideal of a mystery, the pinnacle of tricks. In the hundred-plus years since the publication of the first mystery story, The Murders in the Rue Morgue, enough locked room tricks to depopulate a galaxy have been created. It's no exaggeration to call the locked room an intangible cultural heritage. To be able to tackle one as a great detective is bliss beyond compare. The Glass House Murders, which includes three, feels like a full course meal. The second locked room in particular has a supremely brilliant trick...”
Tsukiyo's speech grew faster as she stood before the door, and her eyes began to unfocus. When Yuma nudged her with his elbow and said “Ms. Aoi,” Tsukiyo started before clearing her throat.
“Pardon me. The first thing we need to ask ourselves is how the culprit locked the door. Unlike in the first case, a poisoning, the second case, which features a victim stabbed multiple times, kerosene poured around to burn the room, and even a message written in blood, obviously couldn't have been created by a remote trick. It's not even worth considering. There are almost no blind spots in this dining room, so we can also discount the possibility that the culprit was actually hiding in the room when we entered and escaped unnoticed. In other words, the culprit was somehow able to lock the door from the outside.”
Tsukiyo logically explained point by point.
“The door's lock is a simple design that requires turning a latch from the inside and hooking it into the protrusion on the door, so there's no possibility of duplicate keys. With such a simple mechanism, the first thing anyone would suspect is a physical trick. Locking the door from the outside using something like string... What is it, Mr. Kagami?”
Tsukiyo frowned when she noticed Kagami step forward and raise his hand.
“We don't know that door was actually locked. It could have been barricaded by something inside the room.”
“Wow!” Tsukiyo exclaimed. “As expect of you, Mr. Kagami, how perceptive. But...”
“But?”
Kagami's thick lips twisted, but Tsukiyo ignored him and pointed to the floor directly in front of the door.
“It is true that there are tricks involving blocking the door to make people falsely believe the door is locked. But in that case, the obstacle should still be there when the door is forced open. So as soon as we entered the second crime scene, I immediately checked the floor here, but I couldn't see the slightest trace of something there.”
“Then maybe it was something that melted and mixed into the water from the sprinklers. Like... a chunk of ice.”
“You think something was there that had enough mass to prevent the door from opening even when several people pushed it as hard as they could, but disintegrated into total non-existence the moment the door opened?”
Faced with that provocative response, Kagami could do nothing but sit quietly, bitterness written across his whole body.
“I'm glad you understand. Now, look here.”
Tsukiyo pointed to the higher of the two protrusions on the door.
“The paint around this protrusion has been peeled off. That was caused by the latch scraping against it when the door was broken down. Thus, the door was locked by this latch, set from the inside.”
“No, Ms. Aoi, it's dangerous to conclude that so readily.”
Kuruma interjected. Unlike when she dealt with Kagami, Tsukiyo bowed respectfully and said “May I have your opinion, sir?”
“The culprit may have set the latch then broken down the door themself, creating those traces.”
“What? Why would they have done that?”
Yumeyomi's eyes widened.
“So that, after we broke it down, we would see those marks and mistakenly conclude the door was locked by the latch. We can't deny the possibility that the culprit is misleading us.”
“No, we can't,” Tsukiyo nodded with some satisfaction. “As expected of Mr. Kuruma, a pointed observation. You could call this a manifestation of the Late Queen Problems described by Norizuki Rintaro in his Early Queen Theory. Well, strictly speaking, the term 'Late Queen Problems' wasn't used in Early Queen Theory, but by Kasai Kiyoshi in-”
“Late Queen? What's that?”
Yumeyomi interrupted Tsukiyo. They looked mutually annoyed with each other.
“In mystery novels, it isn't possible to truly confirm that the solution presented by the detective at the end of the novel is really the truth.”
Kuruma explained on Tsukiyo's behalf.
“In short, within the closed world of a mystery novel, no matter how logically the detective interprets the clues they've obtained, there is no guarantee that those clues weren't forged, which is a major problem.”
Yumeyomi's brows furrowed in confusion. Kuruma opened her mouth to explain further, but Tsukiyo spoke up before he could.
“That's right. The Late Queen Problems are very important to The Glass House Murders. But there's no need to worry about that in this specific case.”
“Obviously. This isn't a mystery novel, it's real life.”
Kuruma muttered to himself. Tsukiyo went on.
“Ms. Tomoe said that Mr. Oita would always lock the dining room from the inside while preparing so that Mr. Kozushima and the guests wouldn't see it.”
At the mention of Madoka's name, Sakaizumi's body trembled slightly.
“In other words, if the culprit had broken the latch on the door ahead of time, Mr. Oita would have noticed.”
“But isn't it possible that the culprit forced their way in after Mr. Oita locked the door, and that was how the latch broke?”
Tsukiyo pointed at Sakyo and said
“That's a good point. However, there were no signs of resistance on Mr. Oita's body, even though he was stabbed from the front. If the culprit had attacked him after breaking down the door, there should have been some traces of him resisting: disheveled clothes, defensive wounds... In other words, it's more likely the culprit casually approached Mr. Oita before the door was locked, then attacked him when they saw an opportunity.”
“Then after they killed him like that, they locked the door, forced it open, and broke the latch, then somehow managed to seal the door from the outside...”
Sakyo stopped and shook his head.
“There would be no point to that. I'm sorry for saying strange things.”
“No, it isn't strange at all. The culprit knew I, a great detective, was here. It's possible they would have wanted to create false evidence to confuse my theorizing. That's a common manifestation of the Late Queen Problems.”
Shrugging slightly, Tsukiyo continued.
“However, there is a major problem with that hypothesis. The door was opened quite forcefully, enough to destroy the latch. It would have made a lot of noise.”
“Ah...” went Sakyo.
“Yes, making that false clue would have created the risk that Ms. Tomoe and Mr. Sakaizumi, who were preparing breakfast, would have noticed. I can't imagine the culprit would have taken that risk to leave one false clue. In other words, the culprit must have genuinely locked the door from the outside.”
Tsukiyo flourished her arm.
“So, how did the culprit lock the door. Yuma, any thoughts?”
Yuma, having been engrossed in Tsukiyo's explanations, started and went “Huh?” in a high-pitched voice.
“In a situation like this, it's customary for the detective's assistant to try and develop various theories of their own.”
So the great detective could show off by disproving them? Grumbling to himself, Yuma racked his brains.
“They could have hooked a string on the latch and manipulated it from the outside-”
“We disproved that the day before yesterday. This type of latch, which needs to be rotated 270 degrees, would be difficult to lock from the outside through the use of string. Besides, there are no gaps in this door, so it would be difficult to even move the string from the outside, and there no traces of rubbing on the door or the latch.”
“Then, a magnet or something...”
“I told you, this latch is made of brass. Brass isn't magnetic.”
“Then they used a drone.”
“And how did the drone escape the locked room?”
Yuma, having run out of ideas, furiously shook his head.
“I give up. Even if you say it's got to be some kind of physical trick, if there aren't any gaps in the door, then there's no way to operate the latch from the outside.”
“You're right, there isn't. Besides, if you do something suspicious while standing outside the door, there's a chance someone will see you. That's why the culprit set up a trick before they left the dining room. A trick to lock the door automatically after they escaped.”
“The latch was set automatically?”
When Yuma asked, Tsukiyo replied “Seeing is believing” and returned to the table.
“The trick is simple. It's so simple, once I reveal it, you'll all stomp your feet and yell 'Why didn't I realize something so simple before!?' The culprit used something within the dining room to create a timing device that would automatically lock the door.”
“Something from the dining room? What exactly did they use?”
When Sakyo asked, Tsukiyo opened the lid of the glass sugar bowl on the dining table and picked up something within, saying “This.”
“Sugar...”
Sakyo spoke breathlessly. The object Tsukiyo held between her pale fingers was a large sugar cube for tea or coffee.
For some reason, Tsukiyo picked up the watering can in her other hand and returned to the door, where she knelt down. The bottom latch, still intact, was now at her eye level.
Placing the watering can on the floor, Tsukiyo rotated the latch, now pointing downwards, a bit over 180 degrees clockwise, then pushed the sugar cube into the gap between the latch, which was tilted slightly towards the door, and the wall. The large sugar cube deformed as it was wedged into the narrow space, and the latch rested against it. Even when Tsukiyo let go, the latch didn't move.
“See? Easy. This is what the culprit did.”
“What do you mean? The door isn't locked.”
Yumeyomi asked, and Tsukiyo nodded vigorously.
“You're right, the door isn't locked yet. The culprit set things up like this, opened the door, then left the dining room. Then, the timed ignition device activated and the door was locked.”
“The timed ignition device?”
Yumeyomi sounded suspicious. “That's right,” Tsukiyo replied, picking up the watering can and humming a little tune as she began to pour water onto the latch secured by the sugar cube.
The sugar cube rapidly dissolved as the water poured over it, causing it to shrink. Finally, it slid down through the gap between the latch and the wall. At that moment, the latch, no longer held in place, smoothly fell towards the door, stopping only when it caught on the protrusion.
“See? Done!”
Tsukiyo stopped watering the door and turned back to look at Yuma and the others, who were all frozen in shock.
“It was... that simple...?”
Sakyo jaw was hanging open. Tsukiyo waved the watering can with glee.
“The simpler the trick, the more effective it is. Besides, I don't really like stories that use overly complex physical tricks. They're so hard to understand in a text-only medium. In the end, simple tricks are just better.”
Everyone was so overwhelmed by the unexpected truth that nobody could even retort “This isn't a mystery novel, it's real life.” Meanwhile, Tsukiyo walked with light steps back to the table to return the watering can.
“Ms. Aoi, may I ask something?”
Kuruma put a hand to his temple as though it would help him organize his thoughts.
“So, does this mean the killer planned for the sprinklers to go off from the beginning?”
“Of course. The water from the sprinklers dissolved the sugar, creating the locked room. That is the exact reason the culprit set the fire. They probably only poured kerosene on Mr. Oita to mislead us into thinking they were trying to burn the body and destroy evidence.”
“But how did they start the fire? That would mean the culprit did something to make the fire start after they left. But there were no traces of a candle like there were in the sub-kitchen yesterday on the dining table.”
“You're right. The timed ignition device that left almost no evidence was the biggest mystery of the second case, no, of the entire Glass House Murders. It's a truly brilliant trick.”
Tsukiyo spoke with genuine amusement.
“So you've already figured out what kind of device the culprit used?”
“Of course. Even I was amazed when I realized it. I said earlier that it left almost no evidence, but that isn't really accurate. Far from leaving no traces, the whole device was right in front of us the whole time. It was just so big and so audacious we didn't notice.”
Tsukiyo excitedly rambled on.
“How could the culprit have caused a fire to burst out in a locked room over thirty minutes after they left? That mystery will be solved when we discover the answer to the mystery of why they left bloody letters on the flammable tablecloth.”
“Stop stalling! I've been waiting on edge for so long now, my heart is starting to hurt.”
Yumeyomi clutched the pink dress over her chest. Tsukiyo lowered her eyes to her watch.
“Yes, it's about time, so let's reveal the truth.”
“Time?”
Kuruma cocked his head to the side, and Tsukiyo looked at Yuma.
“Yuma, I'm sorry, but could you help me to open the curtains?”
“Curtains? Why?”
“You'll understand once you see it. Just hurry.”
At Tsukiyo's urging, Yuma opened the curtains. The light of the morning sun rising over the mountains mercilessly poured in. Yuma narrowed his eyes and somehow managed to fully open the curtain.
Yumeyomi protested “It's too bright!”
“I'm sorry, but please bear with it for the moment. But it really is shining. The sun is directly due east of us right now. I understand what Ms. Tomoe meant when she said it was a design flaw. There's no way anyone could eat in here without using blackout curtains.”
Tsukiyo said that with the blinding sun at her back. She looked almost divine, like the lamp of God was shining upon her.
“But do you all remember? Back then, Ms. Tomoe said that eating breakfast in the dining room was 'dangerous'. Not 'difficult', not even 'impossible', but 'dangerous'. Do you think she would say that if it was just because it got too bright?”
“You mean there's something more dangerous about this dining room that just being bright?”
Kuruma asked while holding both hands over his face.
“As expected of Mr. Kuruma. You're exactly right. Everyone, look at the table!”
Tsukiyo shouted. Yuma's eyes were beginning to grow accustomed to the light, so he turned them on the dining table. When he did, he sucked in a gasp. A line of light a few dozen centimeters long was floating over the tablecloth illuminated by the morning sun.
“This is...”
As Yuma spoke, Tsukiyo reached out and touched the window behind him.
“Ms. Tomoe said that this dining room window was designed so that faraway scenery could be seen easily. If you touch it, you'll feel a slight bulge in the middle. The whole window is a giant convex lens.”
“And a convex lens means...”
Yuma's mouth hung wide open.
“Yes, the window is a giant magnifying glass.”
Tsukiyo slapped the glass.
“Moreover, the curve of the glass is matched to the shape of the room. The curve and the bulge coincidentally work together to refract the light most exquisitely, concentrating the morning sun at a particular time each day.”
As Tsukiyo explained, the line of light gradually narrowed and increased in intensity.
Everyone silently focused on the crystallizing morning sun that appeared on the table. Eventually, it consolidated into an oval a few centimeters in diameter, then got too bright to look directly at. At that moment, a scorching hot oval emerged, exactly over the scorch mark on the tablecloth. Tsukiyo placed a folded white towel there. The center of the towel slowly turned brown.
“Only a small portion of the morning sunlight is concentrated in this area, but it's still being focused through a massive pane of glass. It gets pretty hot.”
Yuma remembered how on the first night, he'd moved the sugar bowl and seen a discolored area underneath. Kuruma pointed to the oval on the towel.
“So the flames in the second incident were started by concentrated sunlight?”
“Yes, exactly.”
Tsukiyo turned back to the group.
“Fires like these, caused by sunlight concentrated in one spot by a lens, can be caused even by goldfish bowls or plastic bottles left on a windowsill.”
“Wait a minute,” said Kagami.
“Would something like this really cause a fire? The towel's only changed color a little, it isn't burning.”
“You make a good point, Mr. Kagami.”
Tsukiyo pointed at him, and Kagami flinched and said “I-I do?”
“If a fire would break out just from someone opening the curtains, no matter how carefully the rest of the Tower was constructed, Mr. Kozushima would have fixed the window or taken some other action. This building is in clear violation of the Fire Service Act, and its design is extremely vulnerable to fire. That's why there are fire alarms everywhere.”
“If it wasn't caused by concentrated sunlight, then we're back to square one.”
Sakyo said that, but Tsukiyo wagged her index finger from side to side.
“No, there's no doubt that the sunlight concentrated into this oval was the weapon that started the fire in the locked room. However, the culprit needed to do something else to turn it into flame.”
“Something else?”
Sakyo frowned.
“Yes, the final remaining mystery is why the culprit wrote the message in blood on the tablecloth. That is the final key to uncovering the truth behind this audacious crime.”
Tsukiyo reached over to the table and unfolded the folded towel. A black circle about the size of a softball was drawn in the center of the pure white towel. It had probably been drawn on with the magic marker on the table.
“The color white reflects light well, so not much of the energy of the sunlight was converted into heat. On the other hand, dark colors like black absorb light and retain heat.”
“And moreover,” Tsukiyo said, taking out a white, powdery, snow-like substance from her suit pocket and sprinkling it on the black circle that was already starting to burn in the sunlight.
“The poplar fluff that we thought was meant to symbolize snow actually makes for excellent kindling.”
“So then... you mean to say... the reason they left the message in blood on the dining table...”
Kuruma's voice was worn down and ragged.
“Yes. They painted the tablecloth dark red so it would retain heat and start a fire.”
The moment Tsukiyo opened her hand, the poplar fluff sprinkled on the black circle burst into flames. It was like she was a magician showing her greatest trick.
The flames from the fluff spread to the towel, burning the white fabric.
“During the actual case, the poplar fluff and the tablecloth were both soaked in kerosene, so the flames instantly shot up to the ceiling. The fire alarm went off in an instant, and the sprinklers soaked the whole crime scene in water. Ah, if I leave this alone, it might go off again, actually.”
Tsukiyo picked up the watering can on the table and poured water on the flames, which had spread about thirty centimeters, extinguishing them.
“That is the truth of the second incident. Anyway, it's bright in here. Yuma, close the curtains, would you?”
Overwhelmed by the unexpected truth she had so brilliantly unveiled, Yuma's mind froze, and he could only reply “Ah, ah...” as he closed the curtains. The room, now protected from the scorching sun, looked extremely dark now that their eyes had adapted to the sunlight.
Silence filled the dining room. Everyone kept their distance from the people next to them.
The truth behind the first and second incidents had been revealed. But Tsukiyo still hadn't revealed the most important thing.
“Ms. Aoi...”
Sakaizumi broke the silence in a hushed tone.
“Does this tell us who the culprit is?”
It was the question everyone had been wondering but no one could bring themself to ask. The more they learned, the tenser the air became.
“No, it doesn't.”
Sakaizumi bit his lip before Tsukiyo continued.
“But... It does narrow it down.”
“It narrows it down? How? Who did this!?”
“It's impossible to come up with this trick unless you've witnessed where in this room the morning sun gathers. The culprit also would have experimented to confirm if a dark-colored fabric would actually catch fire. They wouldn't have taken a gamble on it working after committing the murder. But we arrived here on the evening of the first day, which means the guests didn't have a chance to witness this phenomenon before the day of the crime. Despite that, the culprit was able to perform this trick of arson by focused sunlight.”
“So the culprit is someone who has stayed at the Glass Tower before?”
Tsukiyo turned to Kuruma and said
“Yes. Mr. Kuruma, Ms. Yumeyomi, and I set foot in the Glass Tower for the first time three days ago. Mr. Sakaizumi has an alibi for the first incident, so we can remove him from the suspect list as well.”
That meant it was either Kagami or Sakyo who had murdered Oita and Madoka. Which of them should he pin the blame for Kozushima's murder on?
Yuma was breathing heavily and shaking with nerves. He turned and saw Sakaizumi glaring at him with bloodshot eyes. Feeling the knife-edge stare pierce through him, Yuma realized his mistake. It wasn't just Kagami and Sakyo. He was also a suspect.
But when the second and third incidents occurred, he was at the great detective's side. Though she had yet to say so, she knew he had an alibi. She must have known he wasn't the culprit.
...No, was that really the case? Yuma's heart leapt at a sudden foreboding.
He'd let his guard down after she refused to identify him as the culprit when the trick behind the first murder was exposed, but Yuma was sure the great detective had seen through everything. She would accuse him of Kozushima's murder soon enough.
“So, the remaining suspects are Mr. Sakyo, Mr. Kagami, and... Dr. Ichijou.”
Glancing at each person in turn, Sakaizumi muttered dangerously.
“How can we find the culprit among those three?”
“By solving the last case, the case of Ms. Tomoe's murder. If we can identify the truth behind that, the identity of the culprit will become clear.”
“...Then tell me. Who did that to Madoka?”
Tsukiyo said “I understand” and approached the model of the Glass Tower.
“The third locked room was made in Ms. Tomoe's room, the Sixth room. However, we can't strictly call it a locked room, because the window was open.”
Tsukiyo put her finger on the model's window. As it was an accurate model, the window opened about 45 degrees, just like the real thing.
“The Glass Tower is covered with smooth colored glass, making it difficult to climb. In fact, I checked the exterior walls, and there are no signs of anyone having used specialized equipment to climb.”
“Maybe they jumped out the window using a parachute or something?” Yumeyomi offered.
“A parachute needs a certain amount of time to open and slow the wearer's rate of descent to a safe level. It can't be used from this height. Considering the lack of footprints in the snow outside, the possibility of them using a glider or something like that from that height can also be ruled out. And unlike in Mr. Kozushima's case, in the third case, the Sixth key was found inside Ms. Tomoe's headdress. It would be impossible to hide the key there after entering the room without someone seeing.”
“Then how did the culprit lock the room?”
“Yes, that is the biggest mystery of this case. Although the window was open, there is no doubt that this can be treated as a locked room.”
“Ms. Aoi, may I ask a question?” Kuruma asked.
“Of course, Mr. Kuruma, ask away.”
“As an author, I'm not fond of tricks involving advanced technology, but can we deny the trick with the drone Dr. Ichijou mentioned before? Unlike the dining room, the Sixth room had an open window. I'd think a drone could escape from there and return to its user's room without leaving any footprints.”
“I think that would be difficult,” Tsukiyo quietly replied. “With something as large and simple to operate as the latch on the dining room door, it would be simple enough to turn it with a drone. However, the lock on the Sixth room's door is a cylinder lock with a thumbturn on the knob. It's quite small. No matter how advanced a drone the culprit used, I don't believe they could operate it with such precision. For the same reason, we can deny the theory of using a drone to put the key in Ms. Tomoe's headdress.”
“Is that so? I don't know much about drones... I'm sorry to have offered such a strange theory.”
“Not at all. If anyone else has any ideas, please feel free to share with us.”
Tsukiyo looked around at everyone like a math teacher looking for someone to answer the question on the board.
“Ms. Aoi, please, just tell us the truth behind this serial murder case.”
Sakyo pleaded, unable to withstand the pressure of being a suspect any more. Tsukiyo shrugged and reluctantly said
“I suppose there's no other way. In the third case, there are three mysteries besides the creation of the locked room.”
“Three mysteries?” Sakyo asked.
“How did the culprit attack Ms. Tomoe, who had locked herself in her room because she was frightened? Why was Ms. Tomoe dressed in a wedding dress? And why did the culprit go to the trouble of setting a timed ignition device made with a candle in the sub-kitchen?”
Tsukiyo counted off three mysteries.
“Wasn't the ignition device set up because they wanted us to find the body quickly?”
Yumeyomi tilted her head.
“Is that all? Even if the fire alarm hadn't gone off, we would have noticed that Ms. Tomoe didn't come down that morning before too long. If the culprit took the risk of being seen setting the timed ignition device despite that, it's reasonable to assume they had a compelling reason.”
“What was their reason?”
“To open the window.”
Tsukiyo touched the window on the model with her fingertips.
“Because this glass building is vulnerable to fire, it's equipped with sprinklers and other anti-fire measures. One of those measures is that all the guest room windows automatically fully open when the fire alarm goes off, in order to vent smoke.”
“So the culprit set the timed ignition device in the sub-kitchen to open the window of the Sixth room? But the culprit didn't escape through the window, did they?”
“No, they didn't. But the culprit still needed to fully open the window to create a locked room.”
Yumeyomi couldn't keep up with her argument and clammed up, pained expression on her face.
“Well, setting aside why the window needed to be opened, let's move on to the next mystery. Why was Ms. Tomoe in a wedding dress?”
“Wasn't it to show that the motive was revenge for Mashu Shinju, who was killed before she could get married?”
Sakyo didn't sound very confident in his answer.
“That might appear to be the case at first blush. But the poplar fluff we thought was similarly used to represent a victim lost in the snowy mountains was actually used as kindling for a fire. It seems they spread it on Mr. Oita's body to camouflage their intentions. In that case, isn't it reasonable to assume there was a similar hidden intention behind putting the wedding dress on the body? They deliberately stole the wedding dress from the display room and changed the body into it. That would have been much more work and more risk than scattering some poplar fluff around.”
Now that she mentioned it, that was true. But then what reason could there have been for putting the wedding dress on her? As Yuma racked his brains for an answer, Kuruma spoke.
“Ms. Aoi, I've just realized something. May we rewind a bit?”
“Of course, what is it?” Tsukiyo answered with a friendly smile.
“You said earlier that the culprit left a timed ignition device in the sub-kitchen to set off the fire alarm and open the window in the Sixth room. But I don't think the culprit needed to do that. They could have just pressed the button in the Sixth room and opened the window.”
“Bravo!”
Tsukiyo suddenly burst into a one woman applause, stunning Yuma and the others.
“That's it, that's exactly right. That's the biggest clue to solving the third case. The window should have opened if the button in the Sixth room was pressed, and yet the culprit had to take the risk of setting an automatic ignition device in the sub-kitchen. Do you know why, Yuma?”
Tsukiyo asked, sly grin on her face. Yuma didn't panic. His brain cells began to formulate an answer.
“...The culprit couldn't press the button in the Sixth room.”
“And why is that?”
Tsukiyo asked provocatively.
“Because the culprit wasn't in the Sixth room... Because the crime scene wasn't the Sixth room.”
Yuma looked straight at Tsukiyo. She smiled back at him.
“As expected of my Watson. You're completely right.”
“What do you mean, the crime scene wasn't the Sixth room?”
Yumeyomi's voice cracked.
“Exactly what he said. Ms. Tomoe wasn't tortured or murdered in the Sixth room. The culprit didn't escape from a locked room, they moved Ms. Tomoe's body into a locked room.”
Tsukiyo explained, looking at each person in the room in turn.
“In order to move the body without being seen and to make it look like Ms. Tomoe was killed in her own room, it was necessary to open the window in the Sixth room as wide as it would go. The culprit was originally planning to take the key off of Ms. Tomoe's body, go to the Sixth room, and press the button to open the window. However, the culprit wasn't able to find the key to the Sixth room, which was hidden inside her headdress. Even if they came to regret killing her before she told them where the key was, it was too late. So the culprit had no choice but to set off a timed ignition device in the sub-kitchen, opening the window with the fire alarm.”
“How did opening the window let them move the body into the Sixth room!?”
Sakyo demanded, voice full of nerves.
“To answer that, we need to look at why Ms. Tomoe was wearing a wedding dress. That wedding dress was used in Sherlock: The Abominable Bride, a television program starring Sherlock Holmes and John Watson in 19th century London.”
Tsukiyo looked up at a memory.
“Now, you might be thinking 'It's obvious that a show starring Holmes and Watson would be set in the 19th century', but the plot of the BBC's Sherlock is actually about Holmes and the other characters of the Conan Doyle canon living in modern day London. Holmes uses a smartphone to investigate on social media, and Watson writes their adventures in a blog, not a book. To be honest, as a Sherlockian, I frowned when I first heard that, but when I actually sat down and watched, I felt ashamed of how ignorant I'd been, because the show is amazing. In particular, the lead actor, Benedict Cumberbatch, is perfect in the role. If Holmes actually existed in the present day, I'm sure he would-”
Yuma loudly cleared his throat, and Tsukiyo started.
“Well, what I'm getting at is that the wedding dress is very elaborate and quite thick. What effect do you think it would have on a corpse?”
“What effect...? Maybe they were prettying it up as a final show of respect?”
Sakyo was unsure.
“The culprit tortured Ms. Tomoe then stabbed her to death. That's an act of deep hatred. I don't think they would do anything to show respect. But you were right about one thing, Mr. Sakyo. The culprit did want to pretty up the corpse.”
“But the culprit hated Ms. Tomoe, didn't they?”
“Yes, they hated her, yet they cleaned her corpse. The culprit must have had a reason for that contradictory behavior.”
“The blood!?” Kuruma shouted. “Did they need to hide traces of blood?”
“As expected of Mr. Kuruma, mystery writers are truly a different breed. Yes, the culprit needed to stop the blood from leaking out. Although bleeding doesn't occur in great amounts after the heart stops, the body had been cut in multiple places on the thighs and stabbed deeply in the chest. Naturally, blood would have flowed. However, by putting the wedding dress on the body, they could have it absorb the blood for a period of time. In other words, the wedding dress was being used as an impromptu wrapping, encasing the body so the blood wouldn't leak.”
“But it only worked temporarily. When we found Ms. Tomoe, there was blood on the chest of her wedding dress. Why was it necessary to keep the blood inside the dress for such a short period of time?”
When Sakyo asked, Tsukiyo raised her index finger to the height of her face and said:
“Of course, so there wouldn't be any traces of the body being moved.”
“Traces of being moved...”
“Before we realized that Ms. Tomoe was missing, the culprit wanted to move her body to the locked Sixth room. That would make us mistakenly believe that the Sixth room was the crime scene, and that Ms. Tomoe had invited someone she trusted into the room, or that Yuma and Mr. Kuruma had entered the room with the master key. However, if they'd just casually moved the body after torturing it and stabbing it to death, the bloodstains left behind would have exposed the trick. That's why the culprit had Ms. Tomoe wear the wedding dress.”
“How did Madoka get to the Sixth room!? Who killed her!?”
Sakaizumi screamed at her. Tsukiyo took a deep breath.
Finally, the truth behind The Glass House Murders would be revealed. Feeling his body temperature rising, Yuma quietly slipped his hand into his jacket pocket and checked the pill case inside.
“There are several clues that expose the locked room trick used in the third incident. The crime scene wasn't the Sixth room. The body was dressed in a wedding dress so it didn't leave bloodstains when it was moved. The window of the Sixth room needed to be wide open for the trick to be performed. And... the crime took place in the Glass Tower.”
Tsukiyo ran a finger over the decorative glass covering the surface of the model next to her.
“The building where this incident took place isn't an ordinary one. It's a glass spire in the shape of a cone. The most important thing to keep in mind here is that the exterior walls of the Glass Tower aren't vertical, but have a gentle slope to them.”
Tsukiyo took a handkerchief out of her pocket and skillfully folded it into a vague humanoid, which she brought to the model.
“Which is why this happens.”
Tsukiyo let go of the figure, which was pressed to the exterior wall above the Sixth room. Pulled down by gravity, the figure slid down the wall and slipped right into the open window of the Sixth room.
After a few moments of silence, everyone in the room began to chatter. It was such a simple trick. However, Yuma, who had been obsessing over how the culprit was able to escape the Sixth room and create the locked room, never thought of it.
“Special tools would have been needed to climb the smooth outer walls, and they would have left evidence of their use. But if it's just sliding down, they could move the body into the room without leaving any evidence. Thanks to the thick wedding dress, no blood got on the outer wall, and since the windows in the Tower all open from the top, it's extremely likely the body would have been guided by the one in the Sixth room and been funneled inside.”
As Tsukiyo proudly spread her arms, Sakaizumi approached her.
“So who's the culprit!? You said if we solve this case, we'll know who the culprit is!”
“Isn't that obvious?”
As Tsukiyo looked to each person present, she spoke slowly and calmly.
“To slide Ms. Tomoe's body down the outer wall of the Tower and have it land in the Sixth room, it needs to be dropped from directly above the window. The spaces between rooms Two through Eight are ninety degrees each: a quarter of a cylinder, when viewed in a cutaway. In other words, it was dropped from the room four rooms above the Sixth...”
Tsukiyo paused to moisten her thin lips.
“Ms. Tomoe was thrown from the window of the Second room. In other words, the person in the Second room is the culprit.”
The person in the Second room... Everyone turned to the man in question. Kagami Tsuyoshi was silently glaring at Tsukiyo with his hands in his pockets.
“Mr. Kagami, the night before last, when the frightened Ms. Tomoe ran from the game room to hide in her room, you followed right after her. You ran up the stairs, attacked her before she could return to her room, and imprisoned her in the Second room, didn't you? Then you spent the night torturing her until she told you about the dungeon, before finally killing her.”
Kagami bowed his head, saying nothing.
“You sealed off the crime scenes, saying the police's investigation had priority, but you really just didn't want us to find evidence that you were the culprit. At first, you'd only intended to kill Mr. Kozushima, the mastermind behind the illegal human experiments, but when the avalanche fell and the police couldn't arrive, you took advantage of the opportunity to kill Mr. Oita and Ms. Tomoe as well, and even exposed the location of the dungeon. Do I have that right?”
Internally, Yuma was cheering. The great detective believed Kagami was responsible for Kozushima's murder as well. All that was left was to get the pill case on Kagami, and the accusation was sure to stick.
“Just what the hell are you talking about?”
Kagami, who had been listening quietly, gave a theatrical shrug of his large shoulders.
“Shut up and listen for once in your life. This bitch is just talking. I'm a cop. Yeah, I investigated the Mashu Shinju case, but no matter how many people died because've those human experiments, there's no way I'd ever kill Kozushima and the others. If I brought them in alive, the chief'd give me a medal, but if I killed him, I'd be on the hook for murder, and if I killed 'em all, I'd be hanged. It doesn't make any sense.”
That all made sense. Yuma waited with bated breath to see how Tsukiyo would refute his claim.
“Mr. Kagami, did you really come to the Glass Tower as a police detective?”
“...What do you mean?”
“Considering that the culprit chose to commit a series of locked room murders, they clearly have a deep knowledge of the mystery genre.”
“Well then that's me off the hook. I don't care about your dumb mystery crap.”
“Is that so?”
“What are you saying?”
Kagami crinkled his nose.
“You've stayed at the Glass Tower several times in the past, and you were close enough to Mr. Kozushima that he invited you to this event. It's hard to imagine an unpleasable misanthrope like Mr. Kozushima would be so friendly with the detective sent to investigate a serial killing he'd committed.”
“...He just liked me, is all. I was on my best behavior so I could get close to him for the investigation.”
“Yes, he did like you, Mr. Kagami. And the main condition for being able to be liked by Mr. Kozushima is being able to talk to him about mysteries. The same goes for you, doesn't it?”
Yuma started when she suddenly turned to him, but he quickly nodded.
“It's true that we spent a lot of my interview to become his personal physician talking about mysteries, and I do think that's why he liked me...”
Tsukiyo smiled at Kagami and said
“Well?”
“...So what if I know about mysteries? That's not a motive for murder.”
“You were searching for Mashu Shinju... Isn't her name hard to pronounce? Names ending with 'u' are rare, let alone having them for both her family and given names. To be blunt, people aren't given names like that on purpose.”
Yuma was thrown for a loop by the abrupt topic change. But Tsukiyo continued calmly.
“Incidentally, in English-speaking countries, there's a certain female name. 'Margaret'. It's derived from 'margaritári', the Greek word for pearl... or, in Japanese, 'shinju'. And as it happens, Mr. Kagami's last name also translates to English. Kagami means 'mirror'... or, if you say it with a thick enough Japanese accent, 'Millar'.”
“Margaret... Millar.”
Yuma muttered, and Tsukiyo snapped her fingers.
“Yes. Margaret Millar. A female American mystery novelist who, together with her husband Ross Macdonald, produced many wonderful works focused on psychological suspense. She was a master author who won the Edgar Award for Beast in View in 1956, and also received a Grand Master Award from the MWA.”
Tsukiyo, having exposited on the subject of Margaret Millar, locked eyes with Kagami.
“Mr. Kagami, if you were a severe enough mystery maniac, you may have given your child a name derived from a famous mystery writer. You told us the other day you were divorced. Did your ex-wife take your daughter with her?”
Yuma gasped at the shocking revelation. Tsukiyo didn't even pause.
“To begin with, it's strange that a detective from the Prefectural Police's First Investigation Division is investigating Ms. Mashu's case at all. Division One investigates when serious cases like murder have been committed and an investigation headquarters has been established. It's the department that serves as the center of major investigations. I can't imagine you'd be sent to stay up in the mountains over an office lady who went missing.”
Tsukiyo continued speaking lightly to the silent detective.
“Mr. Kagami, you gave up being a detective. So you could focus all your efforts on finding your missing daughter.”
The space was filled with a silence that roared in the ears. Yuma forgot to breathe as he waited for Kagami's answer.
“She was in elementary school...”
His voice was so weak that if they hadn't been listening they would have missed it.
“The last time I saw Shinju, she was in elementary school. My wife got sick of me working like a dog at HQ, so she took her away. I thought she would be happier not seeing her fuckup of an old man, so I just kept paying child support. Even if we couldn't see each other, as long as she was happy, that was fine. But...”
Kagami's face fell with a deep sadness.
“Last year, my wife called me for the first time in ten years. She said Shinju had gone missing while climbing the mountain. I wanted to find her, but I had no experience mountain climbing in winter. I couldn't do anything but wait helpless and frustrated for two weeks, but finally, I got to take a vacation. I thoroughly listened to everything the search parties had to say about where Shinju was, and learned about the Chogatake Spiriting Away incident.”
“And I was convinced that my daughter had come to this Tower.”
Kagami shook violently.
“No... It wasn't that I was convinced. Shinju coming here was just the only way she could still be alive. So I managed to meet Kozushima.”
“You were able to meet Mr. Kozushima, even though he's such a recluse?”
“I was lucky. As you surmised earlier, I'm a pretty big fan of mystery novels, and I have friends I share the interest with. One of them was an acquaintance of Kozushima's. Mystery freak connections. Kozushima was interested in me as a Division One police detective and a fellow mystery fan. I pretended to care about his boasting while hiding the fact that I was a father, and casually asked him about the string of missing persons cases in Chogatake. He played dumb, but I've dealt with enough criminals to know when I'm being lied to. I knew Kozushima was the mastermind behind the Chogatake Spiriting Away incident. And judging by their reactions, I knew the butler and the maid were involved.”
Kagami clenched his fists so tightly they shook.
“Didn't you think about reporting him to the police and having them investigate the Glass Tower?”
“Kozushima's a real big shot around here. His taxes singlehandedly make up a few percentage points of the regional residential tax revenue. There's no way they'd ever authorize a search of his house based on my hunch.”
“And that's why you worked so hard to ingratiate yourself to Mr. Kozushima, to the point where he allowed you to stay at the Glass Tower: so you could search for hard evidence of the Chogatake Spiriting Away incident.”
“Yeah, but even when I snuck out of my room in the middle of the night and searched the Tower, I couldn't find any clues. That's why I thought this event, when there would be so many other guests, would be my chance.”
Tsukiyo nodded.
“I see. So, you poisoned Mr. Kozushima with the pufferfish poison, killed Mr. Oita, and tortured Ms. Tomoe to find out the location of the dungeon before stabbing her to death.”
When Tsukiyo said that, Kagami snorted.
“Hey, great detective. You act like you're so smart, but in reality, you don't know a thing.”
“What do you mean?”
Tsukiyo's head tilted to the side.
“I didn't kill Kozushima. I didn't do anything until after Kozushima was killed and the avalanche prevented the police from coming. I thought this was my only chance to get revenge on the remaining culprits, the butler and the maid, and to find out where Shinju was.”
Yuma stiffened. Tsukiyo frowned.
“Are you really trying to lie about this? You think if you only killed two people, you won't get the death penalty? Are you saying there were two people who hated Mr. Kozushima enough to kill him on the guest list of this event?”
“That isn't so strange. Kozushima was human garbage. There were probably as many people who hated him enough to want to kill him as there are stars in the sky.”
Kagami pointed to each and every person there.
“One of you guys standing around lookin' all innocent is the real culprit behind Kozushima's murder. Who is it? Which of you is a fellow murderer?”
The moment Kagami pointed his finger at him, Yuma tensed his facial muscles to keep his agitation from showing.
It's okay. Kagami's already admitted to killing Oita and Madoka. No one would listen to the words of a murderer. If there was any exception...
Yuma cast a sidelong glance at Tsukiyo. She had her hand on her lips, pondering with a grim expression.
It would be dangerous to give the great detective any more time to think. He had to bring the case to a close quickly. As Yuma gently slipped a hand into his pocket, a voice that sounded like it came from the depths of hell shook the air in the dining room.
“It was you...”
Sakaizumi's lips peeled back until his gums were visible, and his bloodshot eyes were laser-focused on Kagami. His appearance was reminiscent of a starving animal.
“You're the one who killed Madoka!”
Sakaizumi kicked off the floor and attacked Kagami. Caught by surprise, Kagami and Sakaizumi collapsed in a tangle of limbs.
“I'll kill you! I'll kill you!”
Sakaizumi swung a fist down at Kagami's face. Kagami could only cover his face with his arms and scream “Stop! Stop!”
Now! It was now or never! Pulling the pill case from his pocket and hiding it in a fist, Yuma also leapt at Kagami, shouting “You stop!” As he pretended to hold him down, Yuma shoved the pill case into Kagami's pocket.
“Stop it!”
Still on the ground, Kagami kicked Yuma and Sakaizumi away. As Sakaizumi went to attack him again, Yuma shouted “Wait!”
“Why!?” Sakaizumi said, biting his lip.
“He's a murderer who's killed three people. He might have a weapon on him.”
Check his pockets. See what he has. The thought ran through Yuma's head on a loop as he glared at Kagami.
Kagami nervously stood up, a suspicious look on his face, and put his hand in his suit pocket. Sakaizumi tensed.
“What's this?”
Kagami's eyes widened when he saw the pill case in his hand. A dark smile crept across his face.
“I see. So this is the poison that killed Kozushima. You want to make me out to be the one who killed Kozushima no matter what.”
He'd managed to force the pill case onto Kagami. No matter what excuse he made now, the crime of Kozushima's murder would remain squarely on his head. The moment Yuma relaxed, sure his plan had succeeded, Kagami flicked open the case with his thumb.
“I don't care. My only regret is that I couldn't actually kill that bastard with my own two hands. If you insist on giving me the credit for it, I'll wear it as a badge of honor all the way to hell. Now that they're all dead and Shinju's body has been found, nothing else matters... I have no regrets leaving a world without my daughter.”
Kagami didn't show a single sign of hesitation as he emptied the entire pill case into his mouth and swallowed.
Yuma stood, frozen in shock by the unexpected turn of events. After a few seconds, Kagami groaned, clutched his chest, and fell to his knees.
“What... What the hell...?”
Kagami struggled to breathe until he vomited. A foul stench filled the air.
“Ah, ahgh, aaaaaaaaahhhhhh...”
Yuma and the others could only watch as Kagami writhed and vomited.
Soon, his whole body was convulsing violently, then Kagami's hands, which had been clawing at the air, fell limp.
The scene was so horrible that no one could speak. They all stood in silence. The ticking of the clock on the wall was deafening.
“Yuma...”
After several minutes of silence, Tsukiyo mumbled in a hushed voice. Realizing her intentions, Yuma set his jaw and knelt next to Kagami's motionless form. He got vomit on the knee of his jeans, but now was no time to worry about that.
He gently touched Kagami's neck. He felt no pulse in his carotid artery. He wasn't breathing, either.
“...He's dead.”
He was able to squeeze the announcement from his throat. Sakaizumi let out an animalistic roar.
“Don't mess with me! You killed Madoka, and you think you can just run away like that!? Come back and apologize to Madoka properly! You need to atone for your sins! You need to suffer!”
Kuruma and Sakyo desperately held back Sakaizumi as he tried to kick Kagami's corpse.
Yuma stared at Kagami as he listened to Sakaizumi collapse to the floor and sob. His eyes, their pupils fully dilated, stared resentfully at Yuma.
Ah... He'd killed someone again. But it couldn't be helped. Yes, it couldn't be helped...
Nearly crushed beneath the cross of sin he bore, Yuma desperately repeated it to himself.