Stop!! Hibari-kun!

Kousaku, a teenage boy, moves in to the home of his mother's friend after she dies. This friend happens to be a Yakuza boss with four beautiful daughters. Kousaku is surprised to discover that the most beautiful daughter, Hibari, is biologically male. Hibari is also very interested in Kousaku, and so their crazy but happy life together begins.
(Source: Anime News Network)