Kimitsu married Yukiko, his junior from a university club, and has been living an ordinary, mundane life. One day, Ayumi, a friend of Yukiko's and also part of their old circle, comes to stay overnight. The moment Kimitsu sees Ayumi, he falls for her instantly, realizing feelings he's never experienced before. He thinks to himself, "If only Ayumi were my wife..."—tormented by guilt, yet unable to suppress the pounding of his heart. Then one night, an unbelievable situation unfolds: the trains stop running, leaving his wife Yukiko unable to return home. For Kimitsu, this marks the greatest opportunity he's ever had.