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! What was the truth behind Sachi's surprise kiss? Nagi is finally back in the Ama-Umi House, but he's finding it hard to look Sachi in the eye… Can they no longer go back to being friendly siblings? On top of that, when Nagi returns to school, he finds out he's been chosen to represent his class in the “M-1” competition, the centerpiece of the school culture festival. Apparently, legend has it that the winning pair ends up married…!!