My husband brought in another woman while my mother was away, and my mother, who was no longer treated as a partner, had no choice but to eliminate her sexual desire by masturbating. One day, the mother who saw her son masturbating invites her son and crosses the last line. A mother who feels the strong body of her son who grew up to be a full-fledged man with his whole body and is pleased with his son's growth. Mother and child fall into the forbidden immoral act.