After a girl believed to have committed suicide, a deadly death game emerges, revealing a chilling challenge. Participants, armed with a handgun and knife, must fight in a colosseum until only one survives. When high schooler Yuuto discovers the 'Collesseum' app, he realizes the game's dark origins and finds that a classmate, Tsukishima Io, is involved. Determined to aid Io from the outside, Yuuto and his peers strive to unravel the game's mysteries. As they uncover a shocking revelation linking all players, the harrowing truth unravels before them.