On September 1st, the first day after summer vacation, I went to the literature club room after school to find Mitsumura looking through a part-time job magazine with a serious look on her face. When she noticed me in the doorway, she beckoned me over and showed me a troubled expression.
“I'm thinking about getting a part-time job, but what should I do? I'm not sure whether I want to work at a bakery or a cafe.”
She was pretty carefree for a student with looming entrance exams.
“The same applies to you, doesn't it?” Mitsumura retorted.
“Yes,” I said, feeling myself about to cry.
In the end, I had barely studied at all during summer vacation. Last month, I was caught up in a serial locked room murder case in Yatsuwako Village. Five days after the case was solved by Mitsumura's deductions, the eight day long festival finally came to an end and we were freed from the curse. Of course, I had known for a while by then that the curse was nothing more than superstition, but I still broke out in a sweat when I cut through the wire mesh sealing us in the cave and took my first step back outside the village. When we emerged from the cave for the first time in eight days and looked up at the bright blue summer sky, we realized that the incident was truly, finally over. The summer air was so refreshing. It was so refreshing that I lost all motive to study for my entrance exams. Well, either that or I never had any to begin with. That's actually the prevalent theory.
Incidentally, the third daughter of the Monokaki Family, Fumika Monokaki, was found in Tokyo. Apparently, she'd just run away from home. She was now living in the Monokaki mansion, but she said she had no interest in writing any more novels. I was just glad she was safe.
But just because the case was solved doesn't mean everything was over.
I opened a news site on my smartphone. There was an article about a murder that had happened just that morning. The victim was a famous author of locked room murder mysteries.
Teika Ojou's hunt for mystery writers continued. Or rather, it had only now begun in earnest.
That day, right after she finished confessing to her motive, Teika pulled out a gun. While we were all recoiling at the sight, she leisurely made her escape. She ran into the underground limestone cavern beyond the forbidden door, and from there into the outside... where she rode away in a small balloon she'd hidden there, just like the Magician Under the Moonlight.
“I doubt we'll ever meet again,” Teika shouted back as she rose into the air. “I'll publish more novels now an' again, so give 'em a read if you like.”
Of course, as a serial killer, no publisher would ever touch any of Teika's works again. But she could still self-publish them on the internet. She wasn't interested in money. She just wanted the world to know that a writer named Teika Ojou had found a new trick.
I gave a small sigh. I couldn't sympathize with her motive at all. I'd been a member of the literature club since middle school, so I'd written a few mysteries, but I never once thought the same way as Teika. Of course, I'd also never taken mystery writing seriously. Would someone who was serious about mysteries be able to understand her mind?
“But this is a problem,” I said. “If things continue like this, all of the mystery writers in the world will be killed.”
In the Yatsuwako Village serial murder case, a young man named Murawaka had been burned to death in the Locked Room of Human Combustion. Thinking back, he was a recently debuted locked room mystery novelist. Teika's main reason for killing him was probably to create a closed circle using the fear of the curse, but she may have had another motive. The motive to kill a talented author who may have come up with a brilliant new trick in the future.
Saboten Iyokawa was the same. The police investigation had revealed that she was a famous locked room agent, but of course, Teika probably hadn't known that. Teika killed Saboten to frame her for the crimes temporarily to make everyone let their guard down. She needed Mei to set up the Summer Hina dolls in the living room and Camembert to practice his guitar in the garden. If the murder case was officially still ongoing, there was no guarantee those two would behave as normal.
In other words, it was done so she could carry out the trick of the Ninth Locked Room without concern, but Teika probably had another reason beyond that. She wanted to erase the existence of Saboten Iyokawa, officially another locked room mystery novelist, from the world.
A dry smile automatically formed on my face. She really was indiscriminate. She wanted to kill every locked room author in the world.
Of course, writers who had no talent and writers who didn't write locked rooms weren't on her list and would survive. But there was no point to keeping such writers around. At least, not to me, who wanted to read about locked rooms.
But if she were to succeed, then Teika's own novels would be the only place left to find quality new locked room mysteries. Of course, I was reluctant to read anything written by a serial killer, but I was sure I'd crave it like the addict I was. That was what she wanted. Teika must have had that reaction in mind when she came up with this plan.
But Mitsumura responded to me nonchalantly.
“You'll probably be okay,” she said, stroking the black hair hanging over her summer tanned shoulders. “Because Miss Teika's plan will never succeed.”
“What makes you say that?” I asked. Mitsumura laughed.
“Because there are millions of people in this world who love locked rooms. And every single one of them has the potential to come up with the greatest locked room trick that will ever exist. Because what it takes to create a new trick isn't talent, it's passion. So no matter how many people she kills, she can't kill them all. Somewhere, someone nobody has ever heard of before is dreaming up a new trick as we speak.”
I couldn't help but laugh along with her. I shrugged my shoulders and said
“A joy for the whole human race.”
“Well, maybe more of a joy for the locked room fanatics?”
Mitsumura chuckled.
What she'd said might have just been empty words. But I wanted them to be true. I wanted new tricks to continue to be born into this world forever.
“By the way, changing the subject...”
I suddenly remembered. There was still one more mystery left in the series of locked room murders that had occurred in Yatsuwako Village. Or rather, a mystery had existed before the incident began. The mystery of why Zerohiko Monokaki, the man who could have been called the other culprit of the Yatsuwako Village Octuple Locked Room Murder Case, had committed suicide.
To be honest, I already had an answer. But since motives were a subjective, immaterial thing, there were parts I couldn't be sure were correct.
As I made that excuse to Mitsumura, she looked at me disinterestedly, then leaned on her hand and said “Okay, tell me.” I cleared my throat, then told her the reason why Zerohiko Monokaki had committed suicide.
“I think Zerohiko Monokaki wanted to be the first locked room murderer in Japan. That was the reason he prepared the locked room murder case in Yatsuwako Village. But before he committed the crimes, a girl named Shitsuri Mitsumura stole the title of 'first', and he was so devastated he blew his head off with a revolver.”
Zerohiko Monokaki had committed suicide in the winter of three years ago – specifically, in December of three years and eight months ago. And despite the famous author's shocking end, the incident hardly received any coverage. Because at the time, the world was in an uproar over a different case. That case, of course, being the first ever locked room murder in Japanese history, supposedly committed by Mitsumura. Considering the timing, it was plausible that Zerohiko had committed suicide after hearing the news.
After visiting the Locked Room Library, Zerohiko Monokaki had allowed the locked room to consume his mind. Having read 2,628,000 locked room mystery novels, he had lost the ability to think about anything other than locked rooms.
And so, by chance, Zerohiko Monokaki had visited Yatsuwako Village, where he came up with the trick of the Ninth Locked Room, and devised a plan for a series of locked room murders, with that trick as the centerpiece. Perhaps that was the only fate for a man fascinated by locked rooms. By carrying out his plan, he would break the shell of fiction around the plots of mystery stories, and free the concept of “locked room murders” from that world. It would have been a revolution that would rewrite the values of the world, and Zerohiko dreamed of accomplishing it using the eight final tricks left behind by his beloved Eight Locked Room Masters of the Showa Era, and the Ninth Locked Room that would surpass them all. He dreamed of becoming the most towering figure in the history of locked rooms.
But his dream hadn't come true. Zerohiko Monokaki didn't become Japan's first locked room murderer. No matter how perfect a locked room murder he committed, he would never be anything but an imitation Shitsuri Mitsumura, a mediocre man who could do nothing but bow before his queen.
For a man who'd read 2,628,000 locked room mysteries, that humiliation was something he could never take. So he picked up a revolver. And he blew his head off. That was my theory as to the motive behind Zerohiko Monokaki's suicide.
Mitsumura listened to my explanation with an unmoving pout on her face. She didn't look pleased. When she finally spoke up, she sounded sulky. “To tell you the truth, Kuzushiro, I've been thinking the same thing for a while now.”
“But I just can't accept it. The idea that I caused someone to commit suicide...”
She might have been right. But...
“You could also say that you stopped Zerohiko Monokaki's murder plan.”
If he hadn't committed suicide, Zerohiko Monokaki would have committed locked room murders. If that had happened, Mei and Camembert, who had survived this incident, might have been killed, too. Besides, it was too late for Mitsumura to be upset. Because of the Golden Age of Locked Rooms she had caused, hundreds of people had been murdered in locked rooms in the past three years. And although Teika herself hadn't said anything, that probably wasn't unrelated to the incident in Yatsuwako Village. The locked room murders that occurred in this country every day must have been burning through the remaining trick supply at an alarming rate. That may have been what drove one mystery writer to kill all the others. Because it was hard to exterminate locked room murderers who were scurrying around like rats, but easy to kill someone who just wrote books.
Although I thought all that, I didn't say anything out of consideration for my friend. However, Mitsumura appeared to have realized everything I'd thought a long time ago. She sulked and said “Well, there's no point in talking about Zerohiko Monokaki now,” then closed the part-time job magazine spread out on the table in the club room.
She put the magazine back in her bag. The summer sunlight visible through the window of the club room was starting to turn orange with the evening sky.
“Well, I'm going home. We should study for our entrance exams at least a little.”
“I don't really want to, though.”
“Is that so?”
Mitsumura stood up, then spoke as though she'd suddenly remembered something.
“By the way, Kuzushiro, there's something I wanted to tell you.”
“Tell me?”
“Yes, you.”
Mitsumura gave a gentle cough.
“To be honest, I didn't expect you to see through the misdirection via locked room the way that you did. I didn't think you would be the one to point out the flaw in my theory that Camembert was the culprit. That misdirection used the standard mystery logic of 'the one who could have removed the murder weapon from the scene is the culprit,' so I think an average mystery fan would have fallen for it. But you didn't. So I was a bit surprised. I guess I should praise you.”
I was taken aback for a moment. Then, hesitantly, I asked.
“Are you giving me an unqualified compliment?”
“I wouldn't go that far,” she denied flatly. “I'm still far, far above you. Why, I'm a hundred levels ahead. It's like the difference between a Pomeranian and a Golden Retriever. But, well... how do I put it?”
She averted her eyes and stroked her cheek with her index finger.
“Maybe one day, the day will come... I have some hope now.”
She threw open the door with a loud noise. Then, without turning back to me, she spoke.
“You will solve it, won't you? My locked room?”
That was the promise we'd made.
I would solve the first ever locked room murder in Japan, which she'd allegedly committed three years ago... The locked room nobody else could break. We made that promise here in the literature club room.
The moment I fulfilled that promise, the Golden Age of Locked Rooms would surely come to an end. I would bring an end to this sweet locked room heaven... the most beautiful hell in the world.
“Yes. Leave it to me.”
It wasn't an act for her sake at all; it was pure self-indulgence. I would destroy the locked room Mitsumura had created, and completely defeat her. I was sure the only reason I was still alive was so I could someday witness that scene.
“See you tomorrow, Kuzushiro.”
With that, she left the club room. The sight of her back made me think.
Shitsuri Mitsumura – an angel sent by the God of Locked Rooms. From her back grew beautiful wings as white as snow.
The sight of those white wings filled my heart with relief.
No matter how brilliant a detective was, they couldn't touch those wings, and no matter how brilliant a criminal was, they couldn't tarnish those wings.
Plucking those wings was my job.
And so, I kept thinking. I'd been thinking about the same thing non-stop since I made that promise to her in this club room.
What sort of trick had she used on that day three years ago?
I was searching for that answer – the answer to the locked room that controls the beginning and end of this heaven.