Sayaka spends her days caring for her mother, who has fallen ill. One day, her stepfather begins to look at her with lustful eyes. He strips off her clothes, gags her mouth, and starts assaulting her body. When Sayaka confides in the doctor, she discovers he desires her as well. The doctor diagnoses her stepfather with mental instability, admits him to hospital, and creates a situation where he is left alone with Sayaka. In this new circumstance, a twisted relationship begins to develop.