Kana and Masato are in their fourth year of marriage. They start to see things about each other that they hadn't seen before, and they start arguing more and more over trivial matters... At a time like this, Kana is invited to Tsubasa's house, a former high school classmate whom they met at a class reunion. Tsubasa, who was plain in her school days, has become so beautiful that she is unrecognizable... Soon after, Kana and Masato are invited to Tsubasa's house together, and they hear that the secret to Tsubasa and her husband's happy marriage is swapping spouses...