She was going to identify the culprit of the serial locked room murder case in Yatsuwako Village – the words set us all on edge. “Everyone” being Mei, Camembert, Teika, Chusaita, myself, and Yozuki. Mitsumura was saying that the culprit was one of us six.
Mitsumura looked to each of us in turn and said:
“At first, it appears the suspect list in this case consists of everyone in Yatsuwako village. Even though the bridge connecting this mansion in the Eastern Village and the rest of the populace in the Western Village has been destroyed, it is still possible to travel freely back and forth using the hidden wire bridge. Thus, it is possible that the culprit is one of the villagers. To be even more precise, the underground cavern on the other side of the forbidden door means it's possible the culprit is a total outsider. But neither of those are the case. We can determine this from the circumstances of Ryouichirou's murder. For now, please take a look at this.”
Mitsumura took a piece of paper from her pocket. She placed it on the table for all to see. It was the timeline of the night of Ryouichirou's murder she'd drawn earlier.
Timeline of the Night of the Incident
6:50 P.M.: Yozuki, Teika, and Mei confirm the air rifle's presence in the storeroom.
7:00 P.M.: Yozuki, Teika, Mei, and Camembert move to the living room, Ryouichirou and Chusaita start dinner.
8:00 P.M.: Dinner ends, Camembert moves from the living room to the northern section.
8:05 P.M.: Camembert returns to the living room with his guitar case, moves to the southern section.
8:10 P.M.: Ryouichirou moves to his room in the southern section.
8:15 P.M.: Yozuki, Teika, and Mei start assembling Summer Hina dolls.
9:00 P.M.: Yozuki exits the building via the southern section for a night walk.
9:30 P.M.: Yozuki returns to the living room.
10:00 P.M.: Camembert returns to the living room, still holding his guitar case, moves to northern area.
10:05 P.M.: Camembert returns to the living room and helps assemble the Summer Hina dolls.
10:30 P.M.: Chusaita moves to the northern section to use the bathroom.
10:40 P.M.: Chusaita returns to the living room, moves to the southern section intent on returning to the police box.
11:10 P.M.: Chusaita returns to the living room, asks to use bathroom, returns to northern section.
11:20 P.M.: Chusaita returns to the living room.
12:00 A.M.: Chusaita exits mansion via southern section.
12:05 A.M.: Summer Hina dolls are assembled.
12:10 A.M.: Yozuki, Teika, Mei, and Camembert leave the living room.
“Ryouichirou left the living room and went to the southern section at 8:10 P.M.” Mitsumura said, pointing at the timeline. “Therefore, he was unquestionably not killed until after 8:10 P.M.”
We all nodded. We could understand that much.
“Now, the important part.” Mitsumura pointed to another point on the timeline. “At 6:50 P.M., the murder weapon, the air rifle, was still in the storeroom in the northern section. Dinner started immediately afterwards, and everyone had valid alibis until the end of dinner at 8:00. No one left their seats a single time. In other words, if this was an inside job, the culprit must have gone to retrieve the air rifle after 8:00 P.M. Then...”
She stroked the paper with her fingertips.
“We must also keep in mind that there was always someone in the living room between 8:00 P.M. and midnight, when the security system on the storeroom activated. From 8:00 P.M. to midnight – that is when the crime must have taken place. And as Mei explained before, it is impossible to get to the northern section without passing through the living room. Which means, those in the living room yesterday were unintentionally keeping watch on those who went in and out of the northern section, where the air rifle was kept.”
She was right. The forbidden door in front of the storeroom led to the outside via an underground limestone cave, but the other entrance to the village – the tunnel we passed through when we first arrived, which could be called the main entrance of the village – was blocked by a wire mesh. And when we checked that wire mesh after Ryouichirou's body was discovered, there were no traces that it had been tampered with. Which meant there was no possibility that the culprit had taken the air rifle out via the underground and then brought it back into the village through the main entrance. So, as Mitsumura said, there was no way to take the murder weapon without passing through the living room in full view of everyone, which meant this timeline was a record of everyone relevant to the case.
Thus, the theory that the culprit was another villager or an outsider was eliminated. If someone like that had passed through the living room, Yozuki and the others definitely would have noticed them.
“So, what specifically did the culprit do during the crime? Let's ask ourselves that.” Mitsumura stroked her black hair, a small smile dancing on the corners of her mouth. “First, in order to kill Ryouichirou, the culprit must have gone from the living room to the southern section where he was between 8:00 P.M. and midnight. And since they also had to get the air rifle from the storeroom, they would have also had to go to the northern section. In short, the culprit ① Moved to the northern section to get the gun, then ② Returned to the living room and ③ went to the southern section where the victim was.”
So the culprit had to be someone who fulfilled those three requirements in that order. The northern section had no other entrances and fixed windows, so the culprit couldn't have moved directly from the northern section to the southern section via the garden, or vice versa. And since the windows in the northern section didn't open, the culprit couldn't have shot the victim out in the garden from the northern section, either. That meant that, as Mitsumura said, the culprit must have gone from the northern section to the southern section via the living room.
“After killing Ryouichirou, the culprit also had to return the air rifle to the storeroom before midnight, when the security system activated. So the culprit also must have ④ Returned to the living room, and ⑤ gone from there back to the northern section.”
I took another look at Mitsumura's timeline. So, the culprit had gone to the northern section to retrieve the murder weapon, then traveled to the southern section, then gone back to the northern section to return the weapon.
Two people fit the qualifications: Camembert and Chusaita.
“One of them is the culprit,” said Mitsumura. “So, which of them is it? The thing to keep in mind is the size of the air rifle. Including the barrel, the rifle has a length of nearly a full meter. That's pretty big. Too big to hide in your pocket like a handgun.”
That was certainly true. But... wait.
“Isn't that strange?” I asked. “The living room was in full view of everyone. Since the air rifle couldn't have been hidden in your pocket, they must have carried it out in the open. But if they did that, then everyone would have seen the culprit walking into the living room holding a rifle.”
And nobody had mentioned anything about that.
“That does seem to be the case,” Mitsumura said with a solemn nod. “So then, what did the culprit do? How were they able to carry the air rifle without being noticed?”
I thought about it for a moment, and a simple solution came to mind.
“Did they put it inside something?”
“Yes, that's it,” Mitsumura nodded. “And one person had a container perfect for the job. A case over a meter long and about 15 cm deep. That's the perfect size to carry a rifle, isn't it? I'm talking about-”
“The acoustic guitar case!”
Teika shouted out.
“Yes, that's right,” Mitsumura nodded.
“That person put the gun in their guitar case that night and walked right through the living room in full view of everyone. They only pretended their guitar was inside. In other words, there's only one person who could have committed the crime.”
All eyes turned towards the man in question. Mitsumura announced his name.
“Camembert Monokaki. You are the culprit.”
Camembert looked confused for the moment after Mitsumura said his name, then spoke up in a panic.
“Eh? Wait a minute, Mitsumura...”
“As you can see from the timeline,” Mitsumura cut him off, “At 8:05 P.M., Camembert moved from the northern section, through the living room, to the southern section, and it's clearly written here that he was carrying his guitar case at that time. And when he returned from the southern section back to the northern section at 10:00, he was also carrying the case. The only other suspect, Mr. Chusaita, was empty-handed the whole time. It wasn't written on the timeline, and I didn't see it for myself, but I heard that when Mr. Chusaita returned from the bathroom at 10:40 P.M., he was wiping his hands with a handkerchief, and when he went back at 11:10 P.M., he pressed his hands together and said 'I'm ashamed'. In short, Camembert is the only person in the entire world who could taken the air rifle from the storeroom in the northern section to the southern section and then returned it after the crime.”
Camembert was visibly shaken by her words, but he quickly gave an overdramatic shrug of his shoulders.
“...That's not true. What are you even talking about, Mitsumura?” His voice was obviously full of false bravado. “I really did go and play the guitar. That means the thing inside my guitar case was a real guitar. Not a gun.”
Mitsumura easily dismissed Camembert's rebuttal. “What a pathetic excuse,” she said, a cool smile on her face.
“First of all, that's unnatural in and of itself. Why would you be casually practicing your guitar in the middle of an ongoing serial murder case? Nobody would do that, right? There can only be one possible reason. You are the culprit, and you needed a case to put the air rifle in to commit the crimes. So even though it was a bit unusual, you pretended to practice your guitar.”
“No, that isn't it... That's not it,” Camembert pleaded, steadily losing his composure. “I really do play the guitar as a hobby. I just love the guitar so much... I really do play it every night. Ah, that's right! Everyone! You know that! I take the guitar out to play it every night, don't I?”
Camembert looked desperately at the others. But everyone either looked away or shook their heads. Not a single person knew what he was talking about.
“What... Why...?” His face fell into the pit of despair. He faintly asked “Believe me... Why doesn't anyone believe me? I really didn't kill anyone...”
A heavy silence fell over the room.
But amidst all that, I was the only one held in the grips of confusion.
Something was wrong... No, everything about this was wrong. How could things have turned out like this?
Because...
Shitsuri Mitsumura's reasoning was completely flawed.
I stared at her profile as she explained her reasoning. She didn't appear for a second to doubt that she was right. Could it be... she really hadn't noticed? Her own logic had a massive contradiction.
If that was the case... Wouldn't that be too dumb?
I felt intensely disappointed. The girl I knew would have never made this mistake.
But even with that being the case, what could I do? Mitsumura's answer was wrong. But the path she'd taken up to this point was correct. And if that was the case, then there was no culprit. No one, insider or outsider, could have killed Ryouichirou. It was an impossible crime.
The moment the thought occurred, an intense flash of lightning ran through my skull. An impossible crime... I see. If that was the case, then
This was a locked room murder.
I don't mean the seventh locked room, the Locked Room of Four Color Boxes, or the eighth locked room, the Locked Underground Maze. I had discovered the Ninth Locked Room. There were nine locked rooms in the Yatsuwako Village Octuple Locked Room Murder Case.
But if that was the case, there was nothing I could do in the face of a locked room that strong. It was completely impossible. So, purely out of habit, I turned to her, but she was still interrogating Camembert without a care it the world.
I felt miserable. Ahh... How absurd. I never wanted to see her like this.
Because she's the girl I admire. The angel of the locked room. But the pure white wings had been ripped from her back, exposing her for the pitiful existence she was. She was like an insect, crawling in the dirt. I wish she'd disappear – that thought came from the bottom of my heart. Before she could humiliate herself any further... Just disappear.
Then, as if she'd noticed my gaze, Mitsumura spun towards me and locked her eyes with mine. A grin curved her lips.
“You look like you have something to say, Kuzushiro.”
“Yeah, I do.” I realized my voice was strained. “I'm disappointed in you.”
“Disappointed? That's a bit harsh.” She stroked her hair and flashed me a sickening grin. “Could it be that you've noticed? The decisive... The insurmountable contradiction in my theory?”
“Huhwha?”
A strange noise came unbidden from within me. Everyone else was staring at her in confusion.
“...What do you mean?”
Finally, Yozuki spoke up as if she couldn't take it any longer. Mitsumura just shrugged.
“Exactly what I said. Camembert isn't actually the culprit.”
Everyone recoiled. It was like a bomb had gone off.
“No, no, hold on just a minute!” Teika shouted in a panic. “Just what are you sayin', Mitsumura?” she asked. “Just a moment ago, you were the one sayin' Camembert WAS the culprit! But now you've completely turned on yourself? I don' get it.”
“A lady is allowed to change her mind,” Mitsumura declared confidently. “In fact, the smarter a person is, the more flexible they are. Since I'm a genius, my stance can turn on a dime.”
“Are you kidding me?”
“Yes, I am. I'm sorry.” Mitsumura bowed her head. She then profusely apologized to Camembert, who was still pale and shaking.
“But this was a necessary act.”
“A necessary act?”
“Yes. You could call it my declaration of war on the culprit.”
Mitsumura looked at everyone. Her eyes were on the boundary between “cool” and “chilling”.
“I saw through all your tricks a long time ago. You must have been smirking to yourself when you heard me name Camembert as the culprit, but I was the one laughing at how pathetic you are. I am, in a word, superior to you. And for picking a fight with one so far above your station, the only appropriate punishment is to be completely crushed.”
Mitsumura told everyone.
“I'll say it again, Camembert is not the culprit. Everything I just said is a trap laid out by the real culprit. They were trying to frame Camembert in a most sneaky way. That's why I played along – with the culprit's misdirection.”
“The culprit's misdirection?” Yozuki asked.
Mitsumura nodded.
“Yes, a misdirection using a locked room trick.”
“A misdirection using a locked room trick” – We all looked confused at the new puzzle she'd suddenly provided us.
Mei was the first to find her voice.
“What sort of misdirection was it?”
“That is the question, isn't it? Let's start with the basics,” Mitsumura said. “The sorts of logic used to identify the culprit of a mystery can be divided into two broad types: the 'A is the only person who could have done action B' thread, and the 'A is the only person who would have needed to do action B' thread. The former approaches the case through purely physical elements, while the latter takes a more psychological approach. In the latter case, anyone could have done action B, but only A would have needed to, ergo A is the culprit. But the important thing is that anyone was physically capable of doing action B. They didn't need to, but they could have. Therefore, the possibility that 'the culprit did action B for the specific purpose of making the detective deduce that A is the culprit' always exists. But what about the other possibility?”
Mitsumura looked out over her audience.
“In that case, A is the only person who could have performed action B, so there is no possibility that the true culprit acted to lead a false trail... Is the assumption. But there are exceptions. If there is a trick that could have been used to allow someone other than A to perform action B. After all, the whole point of tricks is to allow people to do impossible things.”
Mitsumura gave an angelic smile.
“And that's just what our culprit did. They used a locked room trick to make the impossible possible. They created this false solution using a locked room trick.”
Everyone groaned at Mitsumura's explanation. “I kinda get it, but I also don't,” said Yozuki.
“In the first place,” Mei said, raising her hand, “When did the culprit use a locked room trick? In the case where Ryouichirou was killed, it doesn't look like there were any more locked rooms anywhere.”
It was true that, in the case of Ryouichirou's murder, there didn't appear to be any locked rooms except for the Locked Underground Maze, which had already been solved.
“That's what an amateur would think,” said Mitsumura.
“I'm sorry...”
“It was just a joke, lighten up. But, well,” Mitsumura glanced at me. “I'm tired, so Kuzushiro will explain it. After all, you also noticed the use of a locked room trick for misdirection, didn't you?”
I froze when she suddenly thrust the responsibility on me. But I steeled myself. As she'd said, I had noticed the existence of the Ninth Locked Room.
So I told them.
“It might be difficult to notice, but there is one more locked room in this case,” I began, my voice tense. “Because there were always people in the living room, the entrance to the northern section where the murder weapon was kept was under constant surveillance. So, the northern section was a Broad Locked Room. And because Camembert was the only one who could have taken the murder weapon out of the 'locked' northern section, we inevitably concluded that he was the culprit. In other words, the physical deduction path showed that he was the only one who could have committed the crime.”
“I see, so since the murder weapon was kept in a locked room, the suspects were narrowed down to one,” said Teika.
But then she frowned and hummed in thought.
“But doesn't that mean Camembert is the culprit after all?”
Camembert's face once again went pale. But Teika was right that, if you thought about it normally, Camembert did seem to be the only suspect.
So I had to nod at her.
“I understand your feelings, Miss Teika. But,” I raised a declarative finger, “what if Camembert also couldn't have committed the crime? That is, what if he couldn't have taken the air rifle, either?”
Everyone was shocked by my question. It was understandable. After all, Mitsumura had just finished proving that Camembert could have taken the air rifle from the storeroom.
Mitsumura herself was looking at me with her arms crossed. It looked like she was assessing my abilities; evaluating me. I nodded at her and continued my reasoning.
“The hint is in the conversation we had while drawing up this timeline,” I said, pointing at the paper. “At that time, I said 'By the way, Yozuki, you went out for a walk at 9:30. Why were you outside that late?', and Yozuki replied 'Because I wanted to feel the night air. Girls have nights like that sometimes.'”
Yozuki looked perplexed by my explanation. She tilted her head.
“Yeah, I'm pretty sure I said something like that, but so what? Does that really clear the suspicion against Camembert?”
“Well, no, the comment itself isn't important. What's important is what happened afterwards: Mei said '“No, you were just skipping work. You thought assembling the Summer Hina dolls was too much trouble,' and Yozuki replied '“No, no, that isn't it! I just wanted a quick change of pace. I wanted to enjoy the night air and listen to the guitar.' When I asked 'The guitar?', Yozuki explained 'Yeah, while I was out walking I saw Camembert playing the guitar. It had some sort of cat pattern on it.'”
Everyone exchanged looks, searching for the meaning in my comment. Yozuki spoke up.
“Yeah, I think I said that.”
“And there you have it,” I nodded. I looked out over my audience and said “From this, we can conclude that Camembert is not the culprit.”
“Eh?”
Yozuki and Mei's voices blended together. Even Camembert said “Huh? How?”
“The important bit is the last thing Yozuki said,” I explained. “Yozuki said she saw Camembert playing the guitar. His favorite guitar, the one with the cat pattern.”
I'd never seen the guitar in person, but it had a pattern like a sitting cat. Camembert had bragged about it to Yozuki just before dinner last night, which was among the details of everyone's actions I'd heard while we were assembling the timeline.
I elaborated.
“Now, on the night of the incident, Yozuki, Miss Teika, and Mei left the storeroom in the northern section at 6:50, and as they were going to the living room, they ran into Camembert, playing that cat patterned guitar. Then, after Camembert put the guitar in its case and left it there in the hall, he accompanied them to the living room. Is that all correct?”
“It is,” said Mei, “but what does any of that have to do with the case?”
“Everything,” I replied. “If Camembert was the culprit, he would have had to carry the murder weapon, the air rifle, in his guitar case, right? And yet, after dinner, Camembert was seen playing the guitar with the cat pattern. That meant the guitar, which had been left in the northern section, was taken outside of the mansion after dinner. As we've established several times over, there are no ways in or out of the mansion in the northern section. So to take the guitar outside, he would have had to move it through the living room to the southern section, in full view of everyone. So, how did Camembert get the guitar to the southern section?”
Everyone exchanged looks. Without waiting for their reply, I said
“It's simple. He put it in his guitar case.”
Everyone recoiled. After dinner, at 8:05 P.M., Camembert passed through the living room, going from the northern section to the southern section. And inside the case we'd thought had contained the air rifle...
“There really was a guitar in there after all?”
I nodded at Mei. That's right. Just as Camembert had claimed from the beginning, there had been nothing in there but a guitar. It was the killer who had tricked us all into thinking the murder weapon was hidden inside.
“And before you ask, there wasn't enough room in that guitar case for it to contain both the guitar and the air rifle.”
Yozuki and the others had seen that when Camembert put the guitar in its case before dinner.
“But what if Camembert had two guitars?” asked Teika. “Then he could'a had an air rifle in the case an' still been seen playin' the second guitar outside the mansion.”
“That isn't possible,” I said. “Because the cat pattern on that guitar was created by a coincidental trick of nature. It's an intricate enough design that you can clearly make out the outline of the cat's ears and tail. The odds of a second guitar with the same image being created are extremely close to zero. That makes the guitar a one-of-a-kind item, something that can't be replicated.”
Which meant that the guitar Yozuki had seen before dinner and the one Camembert played in the garden were the same. And if the guitars were the same, then Camembert must have had the guitar in its case, which meant he had nowhere to carry an air rifle.
“That proves that Camembert couldn't have committed the crime,” I said. “The real culprit knew that Camembert usually kept his guitar in the northern section, and that he was in the habit of practicing it out in the garden after dinner. Which means they could have predicted that he'd go from the northern section to the southern section with his guitar case after dinner. Furthermore, Ryouichirou was in the habit of going to his room in the southern section to work on his novels after dinner, so they also could have predicted that he would stay in the southern section. The culprit was able to use that knowledge to come up with this plan to entrap Camembert. In this village, there is a custom of decorating with Summer Hina dolls on the night of the first day of Obon every year, so it was possible to predict in advance that there would be people in the living room.”
I stopped there. With that, the suspicion against Camembert had been cleared, and everyone was now equally suspicious. And a new problem had arisen. Ryouichirou, who had been in the southern section, had still been shot and killed with the air rifle, even though I'd just proven that nobody, including Camembert, could have taken the rifle from the storeroom in the northern section.
A hidden locked room that nobody could see – the Ninth Locked Room.
“So how did the culprit manage to get it out?”
As I muttered to myself, Mei raised her hand as though she'd just thought of something.
“Maybe it wasn't the air gun that was moved, but the victim.”
“The victim moved?” Yozuki asked, head tilted.
Mei nodded.
“The culprit left the guitar out in the garden, then went to Ryouichirou's room in the southern section and knocked him unconscious. Then they put his body in the guitar case and carried him in it from the southern section to the northern section. Then they killed Ryouichirou using the air rifle in the northern section. That would make the crime possible without needing to take the air rifle out of the northern section.”
As soon as she explained her theory, Camembert started panicking again.
“You mean I'm still the suspect?”
“...It's just a possibility,” said Mei, looking away. Then she turned to me. “What do you think?”
“Sorry, but that's impossible,” I said, shaking my head. “That guitar case is only a meter long and maybe 15 cm deep. It isn't big enough to carry a person inside. And the victim in this case was a person.”
Mei instantly agreed. But even though I'd said all that confidently, I was still at a loss. Even though I was lecturing them all so arrogantly, I didn't know the most important thing: the correct answer.
Moreover, I wasn't entirely convinced that a trick that could explain this perfect locked room even existed.
But when she saw me like that, Mitsumura just laughed.
“Of course it exists. I know what it is.”
She looked calmly at me, at us, and at the real culprit lurking among us as she said:
“The Ninth Locked Room trick does exist. So I'll explain it to you now. The final trick of the Yatsuwako Village locked room murders.”
The trick of the Ninth Locked Room... We all gulped.
“Let's go over the situation one more time,” said the great detective, running her fingers through her long black hair. “This case became a locked room because the living room, which absolutely must be passed through to take the murder weapon from where it was seen before the murder to the crime scene, was observed by several people. In short, there was always somebody in the living room from 8:00 P.M. to midnight, making note of everyone who entered or left the northern section, where the air rifle was kept. That made the northern section into a locked room, impossible to take the gun – that's how it looked. So, the way to break it is extremely simple: We just need a way to take the rifle out of the northern section after 12:10 A.M., when the living room was empty.”
Mitsumura said it so boldly, but we were all stunned silent.
“What are you talking about, Miss Mitsumura?” Mei asked, unable to take it any longer.
“There's no way the air rifle could have been taken after 12:10. After all, the security system activates at midnight, rendering the door unusable.”
That was entirely true. The siren the security system activated was deafeningly loud, and could be heard throughout the entire village, let alone the mansion. But none of the eight shrine maidens who had been up praying to Yatsuwako Myojin all night had heard anything. That proved the culprit never opened the storeroom door after midnight – well, between midnight and 8:00 A.M.
“Oh!” Teika started. “Maybe the culprit went to the storeroom before midnight and took the gun out of the storeroom, without passing through the living room? Then, after midnight, when the witnesses in the living room left, they took the gun out of the northern section and shot Ryouichirou?”
If that was the case, it would appear to explain the locked room. However, Mitsumura shook her head at the theory.
“No, that isn't it, Miss Teika,” she said condescendingly. “Please try actually using your head.”
“Ugh, you're annoying.”
“I'm sorry.” Mitsumura sounded like she was sincerely apologizing.
“But your theory just doesn't hold up under scrutiny. After all, the air rifle was already back in the storeroom by the time the security system was deactivated at 8:00 A.M. Which means that even if the culprit had taken the gun out of the storeroom beforehand, they still would have had to return it afterwards. According to Miss Teika's theory, the air rifle was used in the crime after midnight, so naturally, the security system was already active. If the door to the storeroom were opened to return the gun at that point, the siren would have gone off. In short, it's impossible to return the gun to the storeroom after midnight.”
That was certainly the case. Even Teika, though she looked frustrated, had to admit “Yer right.”
But then what? How could the Ninth Locked Room have been broken? How did the culprit get the rifle out of the storeroom?
“So that's how it is,” Mitsumura said in a calm, even tone. “As I've explained, all the culprit had to do is open the door to the storeroom after midnight and take the gun. Of course, the security system was activated at the time, so the storeroom door couldn't have been opened. The door wasn't locked and could have been opened. So in a sense, what was actually locking the door was the security system. It wasn't actually the northern section that was locked, just the storeroom. So that's all we need to solve. And, as you all know...”
Mitsumura gave a self-satisfied chuckle.
“That is my specialty. I'm probably the best in the world. So naturally, the mystery of the Ninth Locked Room has already been solved.”
“Well then, shall we get right into it? But first, we need to go somewhere else.”
Mitsumura brought everyone to the backroom right outside the storeroom. When Mitsumura pressed the button next to the storeroom door, it opened up.
“Now, let me explain the trick,” she began. “As I've said several times already, if the door to the storeroom is opened between midnight and 8:00 A.M., the security system will caused the siren outside the mansion to blare at full volume. There is no way to deactivate the security system, and the sensors prevent anyone from approaching the siren, so it can't be tampered with in any way. So, how was the culprit able to overcome this obstacle and open the door? That is the mystery of this locked room. And to solve it...”
Mitsumura turned to the east wall of the backroom.
“We must use another unsolved mystery. That forbidden door.”
Mitsumura pointed to the huge metal door on the east wall of the room. It was a pair of automatic doors, 15 meters high and each 7.5 meters wide, opening to the sides like an elevator door.
“Ah, the door that will kill you without exception if you open it,” said Yozuki.
It was, in fact, the infamous door. The culprit opened that door on the night of the incident and carried Kyoujirou's body into the underground cavern. What mysteries did that have left? The culprit opened the door to access the underground cavern so they could create the Locked Room of Four Color Boxes – that was the conclusion we'd all accepted.
When I said all that, Mitsumura nodded at me.
“Yes, but what if that motive was just camouflage? In other words, what if the culprit didn't open the that door to create the seventh locked room, the Locked Room of Four Color Boxes, but to destroy the Ninth Locked Room?”
Open the door to destroy the Ninth Locked Room?
“How would opening that door destroy the locked room?” Yozuki asked. She was getting into it.
“Because of a certain property possessed by the door,” Mitsumura said. “So, my question to you all is: what property does this door possess?”
“That if you open it you'll die without exception?”
It sounded like something out of the occult. Besides, the culprit who opened the door actually wasn't dead, and went on to create the Locked Room of Four Color Boxes. So in reality, it was all delusion.
But thinking about it like that, I suddenly realized. What if the story was completely literal? What if opening the door should have killed someone?
“Poison?”
What if that huge underground cavern on the other side of the door was once filled with poison gas?
The forbidden door was made of metal, so it should have been airtight. So if it was opened, the poison gas would leak out from the underground, poisoning the one who opened the door to death. That was why it was a door that would kill the one who opened it without exception.
When I gave that theory, Mitsumura laughed.
“That isn't a bad idea. But even if the underground was full of poison, it wouldn't explain how to unlock the Ninth Locked Room, would it?”
I groaned. She was completely right...
“But you're close,” said Mitsumura.
“It is true that the culprit used that underground cavern to enter the locked room. And Kuzushiro is correct that 'something' deadly was hidden in that cavern. By using that something, the culprit was able to enter the Ninth Locked Room.”
The question is, what was the something? The storeroom produced a loud siren sound when the door was opened. It was a room locked by sound. What on Earth could have been in there that could clear that hurdle?
We all turned to Mitsumura. She shrugged her shoulders.
“I'm not a pretentious detective, so I'll tell you straight. The culprit used a certain fact of physics.”
“A certain fact?”
“Yes, I'm sure you know it already.”
Mitsumura held up her pointer finger and said mischievously:
“Sound doesn't travel in a vacuum.”
All of our eyes shot wide open. “You aren't serious,” said Teika. Mitsumura just nodded.
“Yatsuwako Village is located inside of a massive limestone cave. Though it isn't as large as the one underground, it's still a vast cavern twenty times the size of the Tokyo Dome – about a square kilometer. So the culprit sucked all the air out of the cave, filling Yatsuwako Village with vacuum. When the culprit opened the door to the storeroom, the siren outside did go off. But because it was in a vacuum, the sound of the siren didn't travel a single inch, and didn't reach a single person's ears. And so, the culprit was able to take the gun right out of the storeroom, even though the security system was active.”
They sucked all the air out of the entire village and created a vacuum? It was such a large-scale trick I couldn't help but gasp.
Large-scale... and absurd.
“Just how could they have gotten all the air out of the cave?”
If, as Mitsumura said, they emptied out the entire village, it would have made the siren completely inaudible, and the Ninth Locked Room would no longer be an obstacle. But the problem was how. Removing the air from a space twenty times the size of the Tokyo Dome wasn't something a person could just do...
“It is possible, using that underground cavern,” said Mitsumura. “There was something deadly hidden in that cavern. What if the 'something' was nothing – in other words, a vacuum? In short, there was no air in that underground cavern. And whereas the underground cavern is enormous, with a base of 25 square kilometers and a height of 100 meters, the aboveground cave where the village is located only as a base of one square kilometers and a height of 25 meters. In other words, that underground cave is 100 times the size of the one containing the village. In that case, what would happen if the door was opened? An elementary school student could tell you that the pressure in the two spaces would be equalized, causing the air pressure in the aboveground cave to be reduced by one-hundredth, to 0.01 atmospheres – a state extremely close to total vacuum. Like this, the culprit was able to create a vacuum in the village through which no sound could pass, even when they opened the locked room.”
I automatically looked up at the ceiling. The ceiling of the backroom was a wire mesh, through which I could see the limestone ceiling of the cave. If the forbidden door were opened, a 15 x 15 meter passage would open in the eastern wall of the backroom, with a hole leading to the underground cavern. That hole would have served as a makeshift air intake, sucking all the air out of the backroom in an instant. But because the ceiling was just mesh, the air would have been instantly replaced by air from the limestone cavern above. So, the air in the limestone cave would have flowed into the backroom through the wire mesh ceiling, and from there into the underground cavern through the hole to the east. It was like the backroom was the nozzle of an enormous vacuum cleaner.
And it wouldn't have taken long to vacuum up the entire village. If there were a can containing one atmosphere of air floating in space, and a hole were drilled in that can, the speed at which the air would flow from the can would be a consistent 340 meters per second, regardless of the size of the hole. And since the caverns were connected by a 15 x 15 meter hole, the volume of air leaking from the village per second was 15 x 15 x 340. Divide that by the volume of the cave containing the village – 1000 x 1000 x 25 – and you got approximately 327. All the air in the village would escape in approximately 327 seconds – less than six minutes. Of course, as the air escaped, the air pressure would drop, slowing the rate at which air passed through the hole. Even so, it would only take six or seven minutes before the village became a vacuum.
And because the air was blowing at such high speeds, naturally, there would have been a powerful gust of wind blowing into the underground cavern, but the culprit likely avoided it by hiding in the depression on the floor. There was a mysterious depression in the floor of the backroom, about two meters in diameter and 50 meters deep. The few seconds between when you hit the button next to the forbidden door and when it actually started opening gave the culprit time to lie down in that depression and avoid being blown away by the wind.
However, the airflow was only fast near the hole, and the airflow throughout the village must have been slower. It was the same as pulling the plug in a bathtub. The water flows slowly everywhere except right near the drain. Compared to the vast cavern containing the village, the hole was extremely small, so the air outside was congested and moved slowly.
This trick also explained why the door to the underground cavern was made of metal. That door had to separate the backroom, filled with air, from the vacuum in the underground. A wooden door wouldn't have been able to withstand the pressure differential and may have been entirely pulled off its hinges. That's why they needed a sturdy, airtight metal door. It was an automatic door that opened with the press of a button, presumably to prevent the door from either being held shut or slammed into the opener's face by the force of the air pressure. The doors to the backroom and the storeroom were probably made of metal for the same reason.
However, I didn't think that the door to the storeroom was airtight. The backroom had a wire mesh ceiling that allowed direct access to the outside cave, so if the entire village became a vacuum, that naturally included the backroom itself. So after taking out the rifle, they had to let the air back into the room. But if the door to the storeroom was left open at that time, the moment the village stopped being a vacuum, the siren would start ringing out. Therefore, the door had to be left closed while the air was being let back into the room.
But if they did that, then the inside of the storeroom would remain a vacuum, even after the backroom was refilled with air. It was difficult to get air into the storeroom, because the moment the door was opened to let the air in, the security system would have gone off.
If the storeroom door weren't airtight, that problem could be solved. The air from the backroom would have gradually flowed into the vacuum of the storeroom through the gaps in the door.
As to how they restored the air to the village, that was surprisingly simple. In the back of the underground cavern was an enormous square iron door, beyond which lay a massive cave mouth like in the Arabian Nights that led to the outside world. In the process of filling the underground cavern, the air from that gap would flow up into the backroom and from there into the aboveground cave containing the village. In other words, the door in the back of the underground cavern was a second air intake, this one connected to the outside.
The volume of air flowing into the underground cavern from there was 80 meters x 80 meters x 340 meters per second. As the air accumulated in the underground cavern and the air pressure raised, the rate of airflow would have decreased, but it still shouldn't have taken that long to fill the volume of the underground cavern – 50,000 meters x 50,000 meters x 100 meters. A quick back of the napkin calculation gave somewhere between 30 and 40 minutes.
And there was one other thing. I finally understood the meaning of the warning attached to the door in the backroom - “This door will kill whoever opens it without exception.” If that door was opened, the entire village would become a vacuum, and whoever opened it would die. In fact, all of the villagers would die. So that the door would kill whoever opened it wasn't a curse or a threat, but a neutral warning.
But it did raise a question.
“Why didn't the culprit die when they opened the door?”
The culprit, having opened the door, must have been exposed to vacuum. And when the entire village became a vacuum, the villagers would have also been exposed to the vacuum. That included the Monokaki Family, myself, and Mitsumura...
“Oh, that was nothing,” Mitsumura said nonchalantly. “First, the culprit. The reason they were safe is because they were wearing a space suit.”
“A space suit?”
“Yes, the one that was in the archive.”
I felt my eyes go wide. There had been a space suit on display in the archive, and Camembert had told me it was the real thing. I never imagined it had been used in the crime.
“Yes, the culprit wore a space suit to protect themself from the vacuum. They must have also put Ryouichirou in an airtight plastic box after rendering him unconscious with drugs.”
“They put Ryouichirou in a box?” I asked Mitsumura, confused. “Why did they need to do that?”
“Because they needed to create a vacuum in the village – and they could only use this trick once,” Mitsumura explained. “Once the door in the back of the underground cavern was opened and the air was let back into the village, it could never be removed again. Because there was only one cave full of vacuum to empty it into. But after the culprit took the air rifle out of the storeroom, they had to return it, meaning they had to open the storeroom door twice. But if the door was opened while the village wasn't a vacuum, the siren would have sounded, so the gun had to be taken out and returned while the village was still a vacuum. What I'm getting at is that the gun couldn't have been taken from the backroom. If the backroom door had been opened, the inside of the mansion would have become a vacuum, and everyone inside would have died. That's why the killer brought the victim into the backroom and shot him there. But if the victim had been exposed to the vacuum, the corpse would have shown signs of vacuum exposure, giving away the trick. So, the culprit shot through the plastic box and hit the victim in the chest. Of course, the bullet hole in the box would have let the air out, so they must have instantly sealed it shut with duct tape.”
I see. So that's what the killer did.
“And the reason the rest of the villagers survived was because of the village's unique customs.”
I asked the obvious question. “Unique customs?” Mitsumura nodded and once again raised her right index finger.
“The custom of only building box-shaped houses.”
My headed tilted over. It was true that Yatsuwako Village only featured box-shaped houses, but how had that saved the villagers?
“You don't get it? All of the box-shaped houses in this village are made of stone and covered in plaster to ensure that they're airtight,” said Mitsumura. “The doors are also airtight and made of metal, and the windows are all made of reinforced glass.”
“Come to think of it,” Yozuki chimed in, “When I found Funika's body in the Locked Villa, I tried to break the window with a rock, but I couldn't even scratch it. Then Mr. Chusaita told me that all of the exterior windows in the entire village are made of reinforced glass.”
Chusaita nodded.
“Yes, I did say all that.”
“And also, when I went for a walk that morning, I noticed that all the houses had their front doors open. When I asked why that was, Mr. Chusaita said that since the people kept their doors closed all night, they used up the oxygen in their houses, so they had to recycle the air to avoid oxygen deprivation.”
“Yes, I did say that.”
“In other words,” Mitsumura took over from Yozuki and Chusaita, “every building in this village is completely airtight. So even though the air outside of the homes was removed, as long as the houses themselves are airtight, the air inside couldn't escape, and the insides remained at one atmosphere of air pressure. The windows are also made of reinforced glass, so they weren't broken by the difference in air pressure. In other words, all of the box-shaped buildings in this village are constructed so that their occupants could survive the village being drained of air.”
We all let out gasps. Did that mean even the existence of the custom of only constructing box-shaped buildings was part of the Ninth Locked Room's trick?
“But,” Yozuki said with a frown, “Weren't the houses in this village made that shape to ward off the kazeitachi?”
“Yes, I'm sure that was the case when the village was first established,” Mitsumura nodded. “So now we must ask ourselves what kind of monster the kazeitachi is. Many supernatural beings of Japanese folklore were originally created as anthropomorphizations of natural phenomenon. That is also the case for the kamaitachi, a monster of the cold winds. I believe the kazeitachi is also a natural phenomenon. Now, ask yourself, what is the kazeitachi, which apparently invades homes through tiny gaps, knocks their inhabitants unconscious, and sometimes even kills them. Doesn't it remind you of something? The clue is right there in the name...”
We all exchanged looks. Finally, Teika timidly asked,
“Could it be gas?”
“Ding ding. I believe it was some sort of toxic volcanic gas,” said Mitsumura. “That huge cave underneath the village... I believe it was once filled with poisonous gas, and sealed in a more primitive manner than it is now. In other words, there used to be a gas outlet in this cave. Since the leading theories are that this village was originally either a bandit hideout or a hidden Christian settlement, I think the village's former lord prepared a trap to annihilate all of the government forces when they came. By unsealing the underground cavern filled with poisonous gas, the village was flooded with gas and their enemies would all die. And the villagers protected themselves from the gas by barricading themselves in airtight houses.”
Then, after the enemies were all dead, the hole leading to the underground was resealed, and the door to the village was left open, giving the gas time to escape the cave.
“Then Zerohiko Monokaki learned about this village, and came up with the idea of using this giant gas pump to create the Ninth Locked Room,” Mitsumura explained, stroking her black hair. “The volcano was likely long dormant by the time he arrived, so he first pumped all the stagnant gas out of the cavern. Of course, he hired a construction team to do that. The work was carried out through the second entrance at the back of the underground cavern. That was connected to a deep hole like a well, so it was probably once a natural exhaust port for the toxic gasses. But it also served as a perfect entrance for the construction workers. And after sucking out all the gas, he then sealed the outlet into the aboveground limestone cavern. As I said before, the outlet was long spent by then, but he needed it completely airtight for his plan, so he needed to have it checked for holes and cracks. All that was left was to construct the mansion and seal the entrance in the back of the underground cavern with that iron door, and the preparations were complete. That door had circular sub-door like a manhole cover, so he could have inserted a hose through that door and pump the air out of the cavern. That was how the limestone cavern was turned into a vacuum for the Ninth Locked Room.”
I pictured the scene in my head and tried to calculate the enormous amount of money it would have cost. Unconsciously, I felt myself begin to smile.
“He really did put in the work,” I said, in awe at it all.
The mansion and the underground cavern below... No, all of Yatsuwako Village and the cavern it was built in could have been said to only exist for the sake of enabling the Ninth Locked Room. That wasn't an exaggeration; it was the plain and simple truth – at least, that was probably the perspective of the man who'd probably devised the trick, Zerohiko Monokaki. According to what Yozuki had heard from Chusaita, Zerohiko had provided incredible amounts of financial support to the village when it was on the verge of being abandoned, on the condition that the villagers never left and the village remained alive. It was clear now that hadn't been an act of kindness. It was just because the structure and customs of the village were convenient for the trick. It was likely that Zerohiko had stumbled upon the village while sightseeing and coincidentally found the cavern full of poison gas, which inspired the trick behind the Ninth Locked Room. And because that trick could only be performed in Yatsuwako Village, he paid to have his “stage” maintained.
To carry out the trick, he'd had all of the air removed from the underground cavern, creating a massive vacuum, and even installed a siren loud enough to be heard anywhere in the village.
From the beginning, I'd wondered why he needed such a loud siren. No matter how you looked at it, it was unnecessary. But that wasn't the case. No matter how obviously unnatural it was, that siren needed to be audible from anywhere in the village. Because we needed to believe that there was no way it could sound without everyone in the mansion and all eight shrine maidens praying in the Western Village hearing.
“The air rifle bein' the murder weapon's the same way,” Teika observed. “It was necessary for the trick. I was curious why Zerohiko had an air rifle, but now it's clear. A regular gunpowder gun wouldn't a' fired in a vacuum.”
I see, I think. Even that had a reason behind it. Of course, it was also impossible to fill the gun with air in a vacuum, so the culprit must have gone in during the day before the murder and filled it.
And the special structure of the mansion, where you couldn't get to the storeroom in the northern section without passing through the living room, was also probably designed specifically to enable this trick. Perhaps even the Monokaki Family's custom of displaying the Summer Hina dolls in the living room was designed for the trick. If there hadn't been people in the living room non-stop, the Ninth Locked Room wouldn't have been a locked room at all.
“So,” Mitsumura concluded, “That is the solution to the Ninth Locked Room. There is only one deduction left to make. I will now tell you who the culprit is.”
“First, we can narrow down the suspects to those who live in the Monokaki mansion,” declared Mitsumura. “My reason is simple. The control panel used to activate the mechanism for the Locked Underground Maze is behind a bookshelf in the library, and moving that bookshelf requires a key to the archive.”
The keyhole was hidden under the floor of the archive, and the bookshelf only moved when the key was turned in the keyhole. So someone who didn't have a key to the archive couldn't have created that locked room. Not only because they needed the key to move the bookshelf in the first place, but because they also needed it to return the bookshelf afterwards.
There were four keys to the library in total. They were held by Mei, Teika, Camembert, and Mitsumura, who had been given the key that had once belonged to Fuichirou. But Mitsumura had been trapped beneath the underground maze with me all night, so we could easily rule her out as a suspect. So, the number of suspects had been narrowed down to three: Mei, Teika, and Camembert. Chusaita, the other villagers, and any outsider were all eliminated.
The air was suffocatingly tense. But Mitsumura didn't even seem to notice and matter-of-factly continued her reasoning.
“Next, we'll rule out Camembert as a suspect. Of course, since the murderer tried to frame him for their crimes, it's obvious that he isn't the culprit. But we can prove that even more decisively. The key is the space suit.”
The one the culprit wore to protect themself (or, apparently, herself) from the vacuum?
“Yes, and the archive where it was kept. The ceiling of that room is just under two meters high, and the space suit was on display on a narrow stage 30 cm off the ground. In other words, the distance from the top of the stage to the ceiling was 170 cm, and naturally, the height of the space suit was less than that. Camembert is over 190 cm tall, so the space suit is too small to fit him. Therefore, he couldn't have worn it.”
I remembered the first time I'd met Camembert, back when Yozuki and I were lost in the woods. His limbs were as long and lean as a model's. I'd been able to tell at a glance that he was over 190 cm tall.
So Camembert wasn't a suspect anymore. That meant that there were only two suspects left. I a quick glance at them: Mei and Teika. They both looked anxious, but one of them must have been acting. One of them was a murderer, though I still struggled to believe it.
I swallowed.
“Shall I continue?” Mitsumura spoke calmly, as though she were trying to dispel the tension. “I will now explain which of the two is the culprit. The key to the entire case is a certain incident. A certain, terrible incident. The incident when Kuzushiro and I were nearly crushed to death underneath the descending ceiling.”
“Yeah... Then,” I groaned. It truly was a terrible incident. But how could it lead us to the culprit?
“It's surprisingly simple,” said Mitsumura. “Because the culprit was the one who lowered the ceiling. And of course, lowering the ceiling required the culprit to use the control panel on the wall of the archive. But do you remember? Doing that required a somewhat unique operation.”
We all looked at each other, then everyone nodded. Of course we remembered. Mitsumura had shown it to us while she was demonstrating the trick of the Locked Underground Maze. It was like this: When you hit the Enter key on the keypad, a random four-digit number appeared on the display, and you had ten seconds to input the same number and hit Enter again. That activated the descending ceiling. Also, at that moment, the door to the room with the descending ceiling locked, trapping anyone in the room, just like Mitsumura and I.
“So in short,” Mitsumura said, “To lower the descending ceiling, the culprit would have had to go to the archive and operate the panel directly. That's because the number to be entered is completely random, and it isn't possible to predict them in advance.”
That was all true. There was no way to do it with a mechanical trick. The culprit had to see the number with their own eyes, then input it.
“So you're saying...”
“Yes, exactly what you think, Kuzushiro,” Mitsumura nodded. “The culprit is the person who was able to move the descending ceiling at that time. Conversely, the person who couldn't have moved the ceiling at that time can't be the culprit.”
“I... see?”
But I was confused. After all, anyone who had a key could have moved the descending ceiling, right? Even though it was a bit complicated, all you had to do was press a few buttons.
When I said that, Mitsumura sighed with exasperation. “That isn't what I meant, Kuzushiro,” she said. It sounded like she was bored with me.
“Can't you use your head a little? Remember? At the time when the descending ceiling was activated... someone had an alibi.”
I let out a breath.
“You mean either Mei or Teika has an alibi for when the ceiling was lowered?”
Mei and Teika both frowned. It looked like neither of them had any idea what she was talking about. What did that mean? How could Mitsumura have known about an alibi that the person who actually had it didn't?
“You say that, but I'm the one who's surprised that she forgot about her alibi.”
Mitsumura sounded genuinely surprised, then coughed.
“Well, I suppose there's no choice. I'll explain for you all. It was at 2:10 P.M. when Kuzushiro and I entered the room with the descending ceiling. At that time, the door still wasn't locked, so the descending ceiling hadn't been activated yet. It was 2:40 when Kuzushiro and I noticed that the ceiling was descending. That means the culprit activated the descending ceiling some time between 2:10 and 2:40. And during that time, one of our two suspects has a perfect alibi. You know what I'm talking about, Yozuki.”
“Huh? I do?” Yozuki looked as surprised as anyone. Then she tilted her head and hummed like a motor in thought. “Hmm... Nope, don't remember.”
Mitsumura insisted “No, you definitely remember.”
“Because at that time, you were playing shogi with a certain someone.”
The certain someone in question started.
“Are you talking about me?”
Mei pointed to herself. At that moment, Yozuki's eyes widened in recognition.
“Now that you mention it, I was playing shogi with Mei around that time. And I got my ass kicked – no, I mean... I won so hard that I caused an overflow error and lost. I think we started at two...”
It seemed that they'd played for the next hour without leaving their seats a single time. Which meant Mei couldn't have moved the descending ceiling.
So...
“So you're the only possible culprit.”
Mitsumura pointed her index finger at the murderer.
“Miss Teika Ojou, the culprit is you.”
The moment Mitsumura made her declaration, all eyes turned to Teika. At the same time, I was extremely confused. Teika was the culprit? That didn't make any sense.
Because...
“Wasn't this an inheritance murder?”
I had assumed from the start that the motive for this murder was Fuichirou Monokaki's enormous inheritance. Was Teika a Monokaki? Maybe an illegitimate child of Fuichirou's?
When I asked, Teika said:
“No, it wasn't for the inheritance. No matter how many of the Monokaki die, I won't see a single yen.”
With that, Teika ran a hand through her dyed brown hair and said
“But I've gotta say, I'm shocked. I didn't expect anyone'd be able to find the truth. As expected of Shitsuri Mitsumura.”
It was as good as a confession. Did that mean she really was the culprit?
I couldn't stop myself from asking.
“If you weren't after the inheritance, then why did you kill everyone?”
Teika gave an ironic smile. Then she scratched her head and put on a bashful expression.
“Hmm, how do I put it? This is more embarrassin' than I thought it'd be. Well, as an author, I've forced many culprits to confess their crimes. I guess they must've all felt the same. A motive is somethin' you should keep in your heart and brood on, on discuss in front of company. It's the sort of thing you should only share with a veteran detective in solemn tones behind the interrogation room glass.”
Having said that, Teika's smile disappeared. At that moment, the air around her suddenly turned cold. Gone was the gregarious author of best-selling novels, and all we saw was the remorseless serial killer who had horrifically murdered all those people in locked rooms.
“Well, to put it briefly,” she said in a voice that chilled us to our souls, “It was because all the members of the Monokaki Family were genius locked room mystery novelists... That was my reason.”
She killed them because they were genius novelists?
“Oh, you've never heard, Kasumi? God has predetermined the number of locked room tricks in existence.”
It was the theory of wealth depletion. The number of locked room tricks in existence is finite, and in the 180 year history of the mystery genre, most of that wealth had already been mined. And as a result, the tricks were drying up.
“Yep, they're all dried up,” Teika said, looking at me like her star pupil. “So now there are only a few new locked room tricks left in the entire world, and we serious mystery novelists are all fightin' over the scraps like people in the desert fighting over water. If someone finds a new trick, it can never be used again. Which is to say, if someone finds a new trick, they've deprived you of the chance to come up with it yourself.”
The life was gradually returning to Teika's body language.
“I spent my life in despair at that. Every time someone else came up with a great trick, I would fall into a depression and wonder why? Why hadn't I been the one to come up with it? And then I'd think 'That trick was supposed to be mine. I was supposed to have come up with it.'”
She grinned broadly.
“But then, on one of those days of desperation, I had an idea. If there was somebody who could have come up with a great trick, I'd just kill 'em before they did. That way, they couldn't take it from me. The tricks I would have come up with the future wouldn't be stolen. Moreover, if I killed all the world's talented mystery writers, the number of locked room tricks left would stop decreasin'. Wouldn't that be great? Then I could take my time findin' the remaining locked room tricks, one by one.”
We were all frozen speechless at Teika's mad logic. Mei asked in a quivering voice,
“That's why you killed the members of the Monokaki Family?”
“Yep, Mei, it is,” Teika said with a solemn nod. “The Monokaki are a family of geniuses – well, except for you an' Camembert. How many new locked room tricks have they discovered? They're like a family a' thieves. They've stolen so many tricks that were supposed to be mine. That's why I couldn't let them go on any longer. I want to kill every talented mystery writer in the world someday, but I decided to start with Fuichirou an' the rest of the Monokaki Family. If you think about it, it's a sign of respect. It's how I recognized their talent.”
After saying that, Teika loudly proclaimed “By carryin' out that plan, I could have created a utopia! I'd kill all of the world's other serious mystery writers, and monopolize all the remaining wealth. I'd have a monopoly on locked room tricks. I would have spent the rest of my life finding every single locked room trick left in the world. I'd find them all. Original tricks that earned universal praise, ridiculous tricks that made people throw their books across the room in rage... They would all be presented to the world as 'Discovered by Teika Ojou'. I'd have all the praise and all the scorn. I'd kill as many people as I needed for that. I'd kill hundreds, thousands if I had too. I wouldn't get jealous of other peoples' talents anymore. I wouldn't let myself be stolen from anymore. The hell of 'someone else coming up with a trick that was supposed to be mine'... I would finally be free of the injustice.”
Her motive was... too bizarre. Everyone remained silent, too afraid to argue with her. Someone said “She's insane.” It took a while before I realized that “someone” was me.
“Killing people over something like that?”
Teika smiled at me coldly. Then she looked at me with scorn.
“I guess so,” she said. “I'm sure someone who's never written a real mystery novel before could never understand.”