The story follows Junpei, a college student who is abducted along with eight other people and forced to play the "Nonary Game," which puts its participants in a life-or-death situation, to escape from a sinking cruise liner. The gameplay alternates between two types of sections: Escape sections, where the player completes puzzles in escape-the-room scenarios; and Novel sections, where the player reads the game's narrative and makes decisions that influence the story, making it branch into six different endings. The whole plot is not revealed in just one playthrough; the player has to reach the one "true" ending to get all the information.