Keita Aono's day begins much like any other, with him late for school. The arrival of a new student, however -- his long-lost friend Hinoki -- means this day will be anything but normal. Keita is unaware of just how strange it will become, and for that he'd probably be grateful. Ever the klutz, Keita accidentally stumbles upon the entrance to an amusement park (Bottom World). Unfortunately, it's been closed due to a series of violent deaths, and he appears likely to become the next victim.