Mizuho Miyanokouji's grandfather leaves an unusual condition in his will: his grandson must enroll at Seio Girls' Academy, the school Mizuho's mother attended and his own ancestors founded. With help from his cousin and childhood friend Mariya Mikado, who already studies there, Mizuho gets a makeover convincing enough to pass and starts attending classes as a girl, keeping the secret from nearly everyone around him. This manga adapts the original visual novel, which also produced an anime series and several OVAs.