Fourteen-year-old Ishii Yui has long wanted to die. She has attempted suicide many times, always failing. Then she wakes up in a vast white room, wearing a gym uniform, with a strange metal collar around her neck. Around her are 332 other people of all ages, all dressed the same. A mechanical voice announces that they will play a series of children’s games—dodgeball, shiritori, rock-paper-scissors—but anyone who loses will have their collar detonate instantly. Only one person will be allowed to leave alive. A screen displays the roster, and Yui sees that every single participant shares the family name Ishii. Faced with imminent death, Yui, who had always wanted to die, finds herself desperately wanting to live for the first time.

Parallel to the death game, the story follows the detective team of Fushimi and Hachisuka. They receive a missing-person request for Ishii Yuuichi, a stage actor famous for his unsettlingly realistic performances. Yuuichi vanished just before the final night of his current play, a show that had already drawn attention for his haunting acting. As the detectives investigate his disappearance, they uncover connections that link the actor to the 333 Ishii prisoners in the white room.

The narrative unfolds across two interwoven threads: the brutal survival contest in the sealed white room, where alliances form and break under the pressure of games that turn innocent childhood pastimes into instruments of death, and the real-world investigation that slowly pieces together the mystery of why these 333 people were chosen. The games force the participants to confront their own memories, identities, and reasons for living. Yui, who once longed for oblivion, learns that even in the most hopeless circumstances, the will to survive can emerge unpredictably. Meanwhile, the detectives’ search for Yuuichi raises deeper questions about the nature of the game, the identity of its orchestrator, and what connects a suicidal teenager, a missing actor, and a roomful of strangers sharing the same surname.