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 Erika are shocked to find that Sosuke has sent them surprise birthday presents. On top of that, their final year of high school life has begun. As Nagi is busy with school, helping Sachi study, and supporting Ai’s acting debut, he comes face-to-face with a major high school event: the class trip! What unexpected twists will this journey hold?!