Natsuko lives with her husband and son. Her husband and son are both busy, leaving Natsuko feeling lonely. She tries to alleviate this loneliness through masturbation. One day, her son accidentally catches her pleasuring herself in the kitchen. One weekend, her husband and son go out, leaving Natsuko exhausted from housework and falling asleep in the living room. Her son returns home early from work and, drawn to his mother's sleeping derrière, begins to stroke his erect penis. Natsuko senses something amiss and wakes up. Startled, her son accidentally ejaculates. Overwhelmed with excitement, he confesses to her, "I can only get aroused by you," and Natsuko, unable to resist his passionate advances, gives in to his desires...