Inheriting her parents' house and living alone without children, Saki lives happily while modestly supporting her office worker husband. One summer day, while doing housework, an unknown intruder unexpectedly barges in to rob her. Although she is extremely scared, Saki realizes that the man is Kyosuke, her husband's younger brother. Out of bad luck with debts and having been fired from his job. Her desperate brother-in-law forces Saki to stay at home. The filthy brother-in-law, who runs back to their parents' house, is a monster with sexual desires.