The game follows Takeshi Kuranari and a boy with amnesia who is referred to as "the Kid", who are trapped inside an underwater theme park together with a group of other people after a leak has flooded parts of the park; they cannot contact people on the surface, and due to high water pressure, the park is estimated to implode after 119 hours. The gameplay consists of the player reading the game's story, at certain points making choices that affect its direction, leading to one of several possible endings.