Yumi lives a life filled with daily masturbation. Possessing an intense libido, she finds her married life unsatisfying and has even considered having an affair, but fears the risks involved. As a result, she sinks deeper into a routine of self-pleasure. One day, however, she accidentally discovers that her son is still a virgin. In that moment, Yumi's heart wavers. She crosses the forbidden line and makes the decision to take her son's virginity. But her son, inheriting Yumi's own bloodline, harbors an overwhelming sexual desire of his own. After his first experience, his lust spirals out of control, drawing Yumi in as his new target. From here begins a shocking and intense story of forbidden passion.