Living together in an apartment, Sayuri's husband was emotionally distant and left her constantly unsatisfied. One night, her son-in-law, curious about his voluptuous stepmother-in-law, caught her masturbating and forcibly made her give him a blowjob. That incident awakened her awareness as a woman, and the very next day, she began developing a close relationship with her son-in-law. The two started slipping sleeping pills to the husband and wife, allowing them to enjoy intense, private moments together. Their forbidden bond gradually deepens, marking the beginning of a new, illicit romance.