Sendo Chihiro, a high school girl, moves from Tokyo to the provincial island of Hanayama after her parents' divorce. There's something strange about the island she moves to. There is blatant discrimination against outsiders, mysterious rituals that suddenly occur and a huge "water tower" built in the middle of the island. One day, a fisherman is stabbed to death in his home. The whole island becomes suspicious of the murderer, and the unexpected culprit is revealed.