“Incidentally,” Yukawa had continued, “this man disappeared on or around March 10. He was about fifty years old. He’d put on a little weight, but was otherwise of average build.”
The body on the Old Edogawa had been found on March 11.
“I’m not sure exactly how it happened, but Ishigami must have learned of Yasuko Hanaoka’s crime, and he’d decided to help her conceal it. He realized that it wouldn’t be enough to simply dispose of the body. If the police should find and identify it, they would inevitably come knocking on her door. And once the questioning started, he wasn’t sure how long she and her daughter could continue pretending they didn’t know anything about it. So, he decided on a different plan: he would kill someone else and then make the corpse look like Shinji Togashi. Then he would slowly reveal to the police when and how the victim had been slain. The more the investigation progressed, the less suspicion would fall on Yasuko Hanaoka. Why should it? She didn’t kill that man by the river. That wasn’t evidence of the murder of Shinji Togashi. You were on an entirely separate case and you didn’t even know it.”
It had been hard to believe that the story Yukawa was telling him could be true. Kusanagi had shaken his head the whole time he was listening to it.
“I think the solution only occurred to Ishigami because he often walked along the river here. He’d had plenty of time to consider the homeless who lived there and their lives. Why were they living at all? Were they just killing time, waiting there for the day when they would eventually die? When they died, would anyone notice? Would anyone care? That’s what I imagine him thinking.”
“So because of that he thought it would be all right to kill one of them?” Kusanagi had asked.
“Certainly not ‘all right.’ But when he was putting his plan together, I’m certain he wouldn’t have forgotten them or their particular circumstances. Remember what I told you. He’s a man capable of doing anything as long as it makes logical sense.”
“And murder is logical?”
“A murdered body was the piece he needed to complete his puzzle.”
The story was, frankly, unbelievable. And hearing Yukawa deliver it, almost as if he was giving a lecture to his students, had made Kusanagi wonder about his friend.
“On the morning after Yasuko Hanaoka killed Shinji Togashi, Ishigami made contact with a homeless man. I’m not sure exactly what transpired between them, but it’s pretty safe to say he offered the man a job. His job description was to first go to the room Shinji Togashi had been renting and hang out there until evening. Ishigami had spent the night before removing all traces of Shinji Togashi’s presence from the room. The only fingerprints and hair that would be left in the room would belong to the homeless man. That night, the man was to go to a place indicated by Ishigami, wearing clothes he had given him.”
“Shinozaki Station?” Kusanagi had asked, but Yukawa had shaken his head.
“No. Probably the stop before that. Mizue.”
“Why Mizue?”
“Ishigami stole a bicycle from Shinozaki station and went to meet the man at Mizue Station. It’s highly likely that Ishigami had left another bicycle there for himself. The two of them rode together to the banks along the Old Edogawa River, where Ishigami killed the man. He smashed his face to hide the fact that he wasn’t Shinji Togashi. Technically, he didn’t have to burn off the man’s fingerprints, because he had already planted them in Togashi’s rented room, which would have led the police to believe that it was Togashi’s body anyway. Yet if he had crushed the man’s face and not removed his fingerprints, leaving the job half done as it were, it would have raised suspicion. His hand was forced by his fear that it might take too long for the police to discover the body’s identity. Which is why he left fingerprints on the bicycle. For the same reason he left the man’s clothes only half burned.”
“But I don’t see the reason why he had to steal a new bicycle for all that.”
“Ishigami stole a new bicycle to hedge his bets.”
“What bets?”
“Ishigami needed to make sure that the police correctly ascertained the time of the homeless man’s murder. He knew the autopsy would reveal a relatively accurate time of death, but he was afraid the body might not get discovered in time, which would make an accurate time of death much harder to determine. If the span of the possible time of death extended to the evening of the day before, in other words, the evening of March 9, that would be very bad for his plan because that was the evening when Togashi actually was killed. Neither Yasuko Hanaoka nor her daughter had an alibi for then. To prevent that from happening, he needed proof that the bicycle had been stolen on or after the tenth. Which is why he chose the one he did—a bicycle that most likely had been left there for less than a day, so the owner would be able to determine roughly when it had been stolen.”
“So the bike came in handy in more than one way for him,” Kusanagi said, smacking himself on the forehead with his own fist.
“I heard that when the bicycle was found both tires were flat. Ishigami did that to prevent someone else from riding off with it. He did everything he could to make sure the Hanaoka’s alibi would stand.”
“But why provide them with such a weak alibi, then? We still haven’t found decisive evidence that they really were at that movie theater.”
“Yet you haven’t been able to find evidence they weren’t there either, have you?” Yukawa had pointed out. “A weak alibi that nevertheless stands up under pressure. That was the trap he laid for you, don’t you see? If he had given them an ironclad alibi, the police would have had to point their suspicions elsewhere. They might even suspect a bait and switch. Someone might even get the bright idea that the victim they’d found wasn’t really Shinji Togashi. Ishigami was afraid of that, so he made everything point to Yasuko Hanaoka as the killer, and Shinji Togashi as the victim. Once the police took the bait, they were hooked.”
Kusanagi had groaned. It was just as Yukawa had said. Once they’d determined that the body was likely Shinji Togashi’s, they started to suspect Yasuko. Why? Because her alibi was flimsy. So they continued suspecting her, which meant they’d never suspected that the body wasn’t that of her ex-husband.
“What a frightening man,” Kusanagi had whispered. And Yukawa had agreed. “It was something you said that led me to the true nature of his scheme, actually.”
“Something I said?”
“Remember what Ishigami told you about his method of designing mathematics exams? About coming at the test-taker from a blind spot created by their own assumptions? Like making an algebra problem look like a geometry problem?”
“Yeah? What about it?”
“It’s the same pattern. He made a trick body look like a trick alibi.”
Kusanagi had practically yelped.
“Remember afterward, when you showed me Ishigami’s work schedule from his school? He’d taken the morning of the tenth as well as the morning of the eleventh off from work. That’s what tipped me off to the fact that the incident Ishigami really wanted to hide had taken place not the night of the tenth, but the night of the ninth.”
That incident was the murder of Shinji Togashi at the hands of Yasuko Hanaoka.