“Just once, I want Rio to pretend she’s my girlfriend!” The couple is stunned by their friend Yuu’s sudden request. While the husband objects, Rio is intrigued after growing bored with her uneventful daily life. He reluctantly lends his wife to his best friend for one occasion, only to become irritated by how happily she prepares for it. He expects her home that night, but Yuu’s mother likes Rio so much that she is invited to stay over. Surely nothing improper could happen... right?