Chapter 63: A Far From Perfect Crime

"The most interesting part of this case is that the culprit performed terribly, committing almost every possible mistake, yet due to various coincidences, every single loophole left behind was inadvertently ignored," Ji I said. "I must say, you are a remarkably lucky murderer, culprit Keita Katase."

"Are you saying I killed Sayo?" Keita Katase panicked, completely forgetting that his father was right there. "I told you, I had no motive to kill her! I knew about the new will!"

"Yes, you knew about the new will, so of course that wasn't the motive," Ji I replied.

"Then tell me, why would I kill my own sister?" Keita Katase retorted.

"Don't rush, let's take it step by step," Ji I answered. "The most puzzling aspect of this case was how impossible it seemed for an outsider to have entered the apartment. But the moment I realized the security guard's testimony was untrustworthy, everything became clear. Ms. Yajima, the person you were truly having an affair with was Mr. Mamoru Imamura, wasn't it?"

Rika Yajima pressed her lips together and said nothing.

"You don't need to deny it. After all, Mr. Imamura's body has already been sent in for examination. Soon, his DNA will be compared with the evidence found in your room."

Rika Yajima's expression turned gloomy, while Shingo Katase looked utterly shocked.

"I must admit, having an affair with a security guard is something very difficult to discover," Ji I said. "As someone who could freely enter and leave the apartment building during working hours without needing to sign in, he naturally escaped notice. With only a few dozen residents in this building, and given Mr. Imamura's familiarity with them, he could easily wait until the dead of night when everyone was fast asleep, leave his post, and head up to your apartment to rendezvous with you.

"Even if a resident entered or left in the middle of the night, they wouldn't pay attention to a security guard's temporary absence; they would naturally assume, 'Ah, he probably went to the restroom,' or something similar. No one would deliberately stand in the lobby at midnight to log exactly how long Mr. Imamura had been away from his post.

"No one realized that the security guard's absence lasted far longer than the mere few minutes it takes for a bathroom break.

"For that, perhaps Ms. Akiba, who occasionally went downstairs for some fresh air in the middle of the night, can bear witness."

Ji I looked toward Reiko Akiba.

Reiko Akiba nodded. "I did indeed go downstairs a few times and find the security guard missing. But since I only stood down there for a short while before returning to my room, just as the inspector said, I didn't think anything of it at all."

"The most fascinating thing is that this tiny coincidence feels like a microcosm of the entire case. Throughout this case, there are blind spots everywhere—flaws so full of loopholes that people simply choose to look right past them," Ji I said.

Ji I turned his gaze back to Keita Katase. "I have to admit, after the DNA evidence in Ms. Yajima's room didn't match yours at all, for a fleeting moment, I almost believed you weren't the killer. After all, with no disputes over a will and no secret affair, you didn't look like a murderer by any stretch of the imagination."

"Yet, I still couldn't shake my unease regarding your reaction when I first mentioned finding evidence of a lover in Ms. Yajima's room. At first, I suspected you were involved with Ms. Yajima, and that your intense reaction stemmed from jealousy-fueled rage. But it wasn't until after Mr. Imamura's death that I understood.

"Your anger wasn't because Ms. Yajima was having an affair with someone else; it was because you were terrified that I would discover their affair, which would shatter the illusion of the apartment building being an airtight locked room. Look at that—two completely unrelated matters, yet people are naturally compelled to tie them together and head down a completely erroneous path. After all, when a charming woman like Ms. Yajima is linked with a successful middle-aged man like yourself, Mr. Keita Katase, people inevitably let their imaginations wander toward scandal."

"This is all pure fantasy on your part. I had absolutely no reason to kill Sayo," Keita Katase argued.

"No, you did," Ji I said. "On the surface, there was no issue of inheritance, nor any exposed affair; you seemed to have no reason to strike. But in reality, you did—you practically told me yourself."

"I told you?"

"Yes, and you even carefully asked me to keep it a secret for you."

Cold sweat broke out on Keita Katase's forehead.

"You see, this is why I say you are a truly lucky killer. Even though you didn't execute any clever trickery and your actions were riddled with flaws, we were somehow guided in entirely different directions. After all, compared to having an affair with your father's mistress, bribing a lawyer to inquire about a will seems like a minor offense, small enough to be completely overlooked, doesn't it?

"Yet, when I looked back on it, I realized: why couldn't that serve as the reason you were being blackmailed by the deceased? Stripping away the more dramatic and eye-catching motives like affairs and inheritance battles, the secret of bribing a lawyer was already more than enough for Sayo to blackmail you. Refusing to be blackmailed and resorting to murder is entirely logical.

"You didn't deliberately mislead our investigation, yet every single clue unwittingly pushed people to jump to wrong conclusions. But obviously, even luck has its limits. What truly convinced me beyond a doubt that you were the killer was the fact that you went out of your way to murder the security guard, Mamoru Imamura," Ji I said.

Keita Katase remained silent.

"Actually, for a time, I almost truly abandoned my suspicion of you. I even started trying to convince myself that your agitated reaction to Ms. Yajima's other lover was merely out of concern for your father being swindled. But if that were the case, I could never figure out where the money the deceased promised to Mr. Imahashi came from.

"Was it Ms. Yajima? Another lover certainly sounds like blackmail-worthy dirt, but the problem was that the deceased had already informed Mr. Imahashi earlier that day that she could secure the funds. In other words, by that point, she had already made contact with the person blackmailing her.

"Yet we found evidence in Ms. Yajima's room of a romantic tryst taking place that very night. Would someone who is actively blackmailing someone else really be in the mood for that kind of thing? That's why my investigation hit a dead end for a while.

"Unfortunately for you, luck may favor you for a moment, but it can never protect you forever. Killing Mr. Imamura was the worst mistake you could have made. The moment I learned Mr. Imamura had been murdered, I understood almost immediately: you were the killer!"

"What does that have to do with me?" Keita Katase protested defensively.

"Because throughout the entire investigation, the only person I told about Ms. Yajima hosting an unlisted visitor who had an intimate encounter that night was you. And you immediately realized why the security guard hadn't been at his post when you entered the building. You knew that if we kept digging, we would eventually uncover the relationship between Mr. Imamura and Ms. Yajima, thereby destroying the premise that the apartment was a locked room inaccessible to outsiders. At that point, you—having no alibi—would likely become the prime target of suspicion once again. You were terrified, so you decided to permanently silence Mr. Imamura."

"You have no proof! You have no proof at all that I killed Sayo!" Keita Katase shouted.

"Proof? Isn't this room overflowing with proof?" Heiji Hattori smiled. "Before your arrival, the inspector had the forensics team thoroughly sweep the room for fingerprints. Your fingerprints are all over the place, sir."

"This is my sister's apartment. What's so strange about my fingerprints being here?" Keita Katase stubbornly contested.

"However, as far as I know, you haven't appeared in the visitor's log once this entire year," Heiji Hattori said, holding up the thick visitor registry. "Unless, of course, you possess some magical method that allows your fingerprints to remain as fresh and clear as if they were left a few days ago?"

Keita Katase froze in place.