At birth, Nagi Umino was switched with another family's baby by mistake. After many years, he finally gets the chance to meet his biological parents. It's on the same day he bumps into Erika Amano, a student from a prestigious all-girls school. Erika pleads with Nagi to act as her fake boyfriend, so she can avoid being married off to a man she does not love. What they later discover is shocking. Nagi and Erika were the babies who were mixed up at birth, and to make things worse, they are already engaged to each other. Their respective families recognize their love, and they begin living together. But despite this, Nagi is secretly in love with a classmate named Segawa Hiro, and Erika wants to defy her father's wishes. Therefore, they both agree to keep their distance, even though they are engaged. Be ready to experience the many screw-ups, comedic moments, and romantic tangles of this chaotic love story. The final two episodes were broadcast together as a one-hour special.