One day, Takeru, a husband who loves his wife Yumi but is troubled by a cuckold fantasy, shows her a wife-swapping site and confides in her troubles. Yumi is confused, but she agrees to go to an offline meetup organized by the site for her husband, with a one-time promise. There, another couple is waiting for her. The other wife is also anxious, but after listening to the organizer Sakurai's lecture, the two couples swap wives and husbands and indulge in obscene intercourse like never before...