Kana and Masato, married for four years, are beginning to notice previously unseen flaws in their relationship, leading to frequent arguments over trivial matters. One day, they receive an invitation to visit the home of Tsubasa, Masato's high school classmate, whom they reunited with at a reunion. Once plain-looking, Tsubasa has transformed into a stunning woman, and her marriage appears deeply affectionate. Hearing that the secret to Tsubasa's happy marriage is couple swapping, Kana and Masato decide to visit her home together to see if it's true. What unfolds there will become a turning point, offering them a new perspective on their own marriage.