Koji still loves his wife Chisato passionately, but recent erection problems leave him anxious that she may abandon him, so he turns to an aphrodisiac. While Koji is away, however, Chisato and her adult son accidentally drink the spiked beverage. Her pussy begins throbbing without being touched as his cock turns rock-hard. Overwhelmed by the heat rushing through them, they gradually cross into a forbidden relationship.