Matsumoto couple visit the husband's family home. Since getting married, wife Mei has felt uneasy about her brother-in-law Naoki's presence. Rumors say he's been living in isolation in a second-floor room for four years. Feeling disturbed by Naoki's eerie existence, Mei stays awake late at night and heads to the kitchen for water—only to suddenly become involved in an unexpected incident. The strange occurrence in the quiet night leads to an event that threatens to destroy the couple's everyday life.