In the fourth year of marriage, Nanami's husband, Koji, has just become independent and is busy with work, coupled with a rut, recently even the couple's conversation has disappeared. In contrast to these two, Hibiki, who has moved into the opposite room, is on good terms with her husband, and whenever she sees the couple, Nanami feels envious. Eventually, Hibiki, who learned about Nanami's cold marital relationship, invites Nanami and Koji to her home and proposes a couple exchange only for the weekend.
