Shūichi Kushimori [Kazunari Ninomiya] lives with his mother Yūko Kushimori [Kumiko Akiyoshi] and his younger stepsister Haruka Kushimori [Anne Suzuki]. One day, his estranged stepfather Ryūji Sone [Kansai Yamamoto] returns home and begins to freeload off the family. After Shūichi notices what appears to be Sone making sexual advances toward Haruka one night, he tries to remove him from the household. Yet he quickly realizes that removing Soneo legally is not possible, because Haruka is his sister in the eyes of the law, and Yūko asks him to endure the situation until Haruka turns fifteen and can choose Yūko as her legal guardian.
Driven by anger and a desire to protect his family, Shūichi conducts thorough research and experimentation on electrocution, and eventually carries out his plan, killing his stepfather. The police declare that Sone died of natural causes, and Shūichi’s alibi checks out—his classmates remember seeing him leave with a half-finished painting and return with it completed later. In a painful reveal, Haruka later confides that Sone had been dying of cancer, a truth that adds another layer to the family’s tangled web of secrets.
Life for Shūichi continues, and he begins a romantic relationship with Noriko Fukuhara. [Aya Matsuura] appears as Noriko, a classmate who becomes part of his мир. Then comes a troubling visit: Takuya Ishioka, a troubled classmate who often skips school, shows up at the convenience store where Shūichi works. Ishioka discovers the bag of items Shūichi used to kill Sone and demands 300,000 yen in a week, threatening to tell the police if he is not paid.
Although Shūichi regrets what he did, he decides to keep Ishioka quiet by orchestrating a staged robbery at his workplace with a fake knife. He stabs Ishioka, making the act appear as self-defense on the security cameras. The investigation is complicated when Masashi Kano [Naomasa Musaka], a police officer who met Shūichi at the time of Sone’s murder, begins to suspect there are inconsistencies in Shūichi’s story.
While walking Noriko home from the train station, Shūichi admits to her that he is a murderer. The police ultimately uncover the truth behind Sone’s death and Ishioka’s involvement, but Kano allows Shūichi to go home on the understanding that he will surrender to authorities the next day. After a normal breakfast with his family, Shūichi visits Noriko at school before class starts. She confirms that she lied for him and will continue to lie in court. Shūichi leaves a tape recording for Noriko as he prepares to face the consequences of his actions.
In a final, devastating turn, Shūichi commits suicide by steering his bike directly into a bus. In his tape recording, he speaks about his favorite things, and Noriko, who had paused coloring her drawing of a future Shūichi blue, stops to listen, the quiet moment underscoring the gravity of the choices that led to this moment.
