Otoboku: Maidens are Falling for Me (2006)

乙女はお姉さまに恋してる

aka Otome wa Boku ni Koishiteru · 少女爱上姐姐 · Otome wa boku ni koishiteru · Otoboku - Maidens Are Falling for Me! · 소녀는 언니를 사랑한다

Mizuho can't believe his ears when Grandpa's will is read out. Grandpa's final wish is for Mizuho to attend the same academy as Mizuho's mother. The catch is it's an all-girls school. With the help of friend Mariya however, he gets a makeover good enough to fool everyone at the academy.