16-year-old super-studier Nagi Umino, second-year student at the Megurogawa Academy high school, was switched at birth. On his way to a dinner to meet his birth parents, he accidentally meets the brash, outspoken, Erika Amano, who is determined to make Nagi her fake boyfriend as she never wants to actually marry. But once Nagi makes it to dinner, he finds his parents have decided to resolve the hospital switch by conveniently having him marry the daughter his birth parents raised…who turns out to be none other than Erika herself!
Nagi and Hiro have broken up! After a shocking Christmas, Nagi works to regain his happiness, and Hiro tells her true feelings to Erika. As the new year rolls around, Nagi finds himself busy with cleaning the Ama-Umi House, the Amano Group year-end party, and Ai-chan’s new year’s concert. Amidst all that, Sachi’s high school entrance exams are closing in…and then she confesses her feelings on New Year’s evening?!