Natsuko, a mother, lives alone with her only son, Naoya, as her husband is away on a long-term business trip. One day, Naoya's friend Makoto comes to stay at the Kayama house. Makoto, who lost his mother at a young age, is drawn to Natsuko's maternal kindness and voluptuous body. Realizing this pure feeling, Natsuko accepts Makoto's hot, engorged penis. From that day on, the two, far apart in age, begin to engage in forbidden sexual intercourse over and over again...