The Mastermind Was Actually Me [Crossover]

After leaving the Ultimate Academy for Gifted Juveniles, Saihara Shuichi finds himself in a new world. His companions are gone, and the people here have never even heard of the killing game. Keeping his suspicions to himself, he tries to fit into this world. To survive, Saihara Shuichi becomes a trainee detective at the Armed Detective Agency. The mastermind keeps testing him, and the world is filled with malice. To protect Yokohama, Saihara Shuichi works hard to track down the mastermind, only to find the trail leading back to himself. Saihara Shuichi: ...? The mastermind is me?! The personality buried beneath the flashback lights gradually resurfaces. Cruel yet innocent, this other self is the truth behind the terrifying incident. [Warning] Protagonist: Saihara Shuichi Original setting: The original personality of Saihara Shuichi before being covered by the flashback lights is an original character. This is a strange story about me framing myself and catching myself. Theme: Humanity's greatest enemy is itself