Kuzu Kazu and her husband live in the same apartment building as the Kanda couple, and the two couples have made it a monthly tradition to get together for drinks. One evening, as the four of them are drinking, the conversation turns to a TV show about spouse swapping—and suddenly, they impulsively decide to try it themselves. However, this swap triggers unexpected complications... Their ordinary routine is completely overturned, and the relationships between the couples take an entirely new turn.