16-year-old super-studier Nagi Umino, second-year student at the Meguro River 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!
Erika feels torn-up after seeing Nagi and Hiro on a date, so she forces him to go on a date with her, too. How will Nagi deal with his new conflicted feelings? Meanwhile, Nagi's grades have taken a hit due to his new living situation, and Hiro is about to learn a major secret... Things start heating up in this tangled love rectangle!