It's check up or health check time. Students line up to get their bodies measured. (A customary thing in Japan at all schools). Kanako has been assigned as a helper, but she faints and misses her opportunity to get a glimpse of beautiful bodies. But she just happens to see Maria, and he has boobs! It turns out that Maria has a twin sister Shizu that is attending the boy side of the school dressed like a boy. The arrangement was made to fulfill their great grandmother's will where the person that can stay without being found out for three years gets the seat of the President of both the boys' and the girls' schools.