Tatsuya is a college student and classmate of Saki as well as her lover. However, he has a special "cuckold" fetish, which one day becomes known to Saki. "... Are you interested, Taku-kun? I'm going to have sex with other people." -The words triggered the two to start swinging with their close senior couple, Marina & Masao. In addition, other men and women join their secret relationship, and the lewd feast gets even more exciting!!!