Kanato and Masato in their fourth year of marriage. They begin to see parts of each other that they couldn't see, and their quarrels only increase over trivial things. At that time, I was invited to the house of Tsubasa, a classmate from school, who I met again at the alumni association. When I was a student, Tsubasa, who was sober, has become so beautiful that it is different ... Soon after, Masato was invited to Tsubasa's house with all his spouses, and he heard that the secret to the couple's marital harmony was a marital exchange ...