Fifty-one-year-old Ritsuko Kawai lets her nephew Mark live in her home. Mark becomes curious about Ritsuko's body, while she, in turn, develops a strong attraction toward him. One day, when Ritsuko exposes herself to Mark, he instantly gets an erection and receives a devoted blowjob from her right then and there. Meanwhile, her son begins to suspect something and calls his mother out, warning her to stop her actions. This situation brings the conflict between family bonds and desire into sharp focus, triggering a new shift in their relationship.