My Best (♀) Butler

Rui would do anything for her younger brother, Kyo—a sensitive boy who became a shut-in after a confession to his male classmate went awry. But she'll need money to care for him, and in a town where the highest of the high are neighborhoods separate from those who are striving just to make ends meet, that's no easy task. Due to her boyish looks, her friend helps her cross-dress to get a job at a host club (of sorts), but when her first interaction goes horribly wrong, she think's it's all over for her...until über-rich boy Tohma saves her. Amused by her story, he makes her an offer she can't resist: Serve as his "male" butler until March of next year, and he'll give her $10,000...but only if her true gender isn't revealed!

(Source: Kodansha USA)