Suspect

Ishigami buys lunch from Yasuko's restaurant, and their morning exchanges become the brightest part of his day. Through these small talks, the distance between their worlds softens and a complicated bond starts to form.

Togashi extorts money from Yasuko and threatens both her and Misato. The confrontation escalates inside Yasuko's apartment, and Togashi is killed by the mother-daughter pair.

Ishigami overhears the commotion from his room and quickly deduces that Togashi has been killed. He volunteers to help the mother and daughter, offering to handle the cleanup and aftermath.

Ishigami disposes of the body and lays out a meticulous plan to cover up the crime. He uses his intellect to orchestrate a defense that keeps Yasuko from being implicated.

When the body turns up and is identified, Yasuko becomes the primary suspect. The police begin to piece together what happened, but the evidence initially points away from a clear conclusion.

Detective Kaoru Utsumi and Detective Shunpei Kusanagi seek help from Professor Manabu Yukawa, hoping his analytical mind can crack the case. Yukawa initially declines, thinking the case lies outside his physics expertise.

Hearing that Ishigami is Yasuko's neighbor, Yukawa changes his mind after reuniting with his former classmate. He agrees to assist the investigation, driven by curiosity and admiration.

Yukawa begins to investigate, methodically cross-checking alibis and examining the mathematical underpinnings of Ishigami's plans. He starts to doubt Ishigami's innocence as the clues mount.

A high-stakes battle of wits ensues as Ishigami tries to protect Yasuko by anticipating Yukawa's moves and refining his cover story. The tension grows as each deduction narrows the possible explanations.

Yukawa finally cracks the case and reveals a sad, shocking truth. The revelation demonstrates Ishigami's strategic manipulation to shield Yasuko, a truth that cannot undo the harm caused.

Despite his reputation for detachment, Yukawa is distraught by the outcome and the human cost of the truth. He contemplates the price of intellect when it fails to offer moral resolution.

The case leaves lingering consequences for Yasuko, Misato, and Ishigami, while the police close the file with a sense of uneasy closure. The film ends on a somber note about truth, protection, and sacrifice.