Stop!! Hibari-kun!

When Kohsaku Sakamoto's mother dies, he is sent to Tokyo to live with the Yakuza boss Ibari Ozora and his four—er... we mean his THREE cute daughters, and one very cute son, Hibari-kun! Yep! The family keeps it a secret, but Hibari, the stylish all-star student and most popular girl at school is actually a boy!

(Source: Peow2)