Nanako is involved in an affair with her stepson, and during her husband's business trips, she repeatedly seeks pleasure through physical encounters with him. However, her life takes a turn when she finds a note in the mailbox stating, "I know everything," throwing her into days of emotional turmoil. One day, while Nanako is alone in the living room, unknown men suddenly break into the house and capture her. They reveal they are aware of her relationship with her stepson, and without giving her any chance to resist, they freely take control of her body, using her as their sex slave.