Three years have passed since Sonoyama married Akiko. Akiko was a virgin, but she was trained by Sonoyama and has now become a ripe woman. Sonoyama has a strong sexual desire and has another mistress named Michiko. One night, he goes to a swapping party at Michiko's urging, and they exchange partners and indulge in an affair, pretending to be married. However, a year later, the couple moves in next door...