Jiro Tenge (???? Tenge Jir??), one of the eldest sons of the moderately wealthy Tenge family, has become an agent working for the United States, and his secret murders are discovered by Ayako Tenge (???? Tenge Ayako?), his youngest sister. This problem is aggravated by her discovery of terrible incestuous affairs in her own family; the wife of her older brother is actually her mother, who has to frequently have sex with Ayako's father, the family patriarch Sakuemon. To hide these secrets, the family—under pressure from Sakuemon and his eldest son Ichiro—decides to keep Ayako locked up in the basement for the rest of her life. Despite the efforts of her mother and younger brother Shiro, she lives for nearly two dozen years under the family's house, while great political and social changes occur above her. Ayako eventually leaves the basement after growing into a beautiful and attractive woman, and seeks affection from others while remaining terrified of the outside world. This sets off a chain reaction of events which spells tragedy for the Tenge family.