Fetixxx!

A girl named Hashinomoto Maaya has long desired to marry her younger brother, Rintarou, believing he felt the same. They had previously attended different elementary and middle schools, but Rintarou is now about to start high school at the same school as Maaya. Excited about their time together, Maaya is surprised when she sees Rintarou. She realizes that when he spoke of wanting to be with her as they grew up, he meant he wanted to be like her. To achieve this, Rintarou begins high school dressed as a girl.