18+ Kamen no Maid Guy

Fujiwara Naeka is a typical 17-year-old high school student. Or so we thought. She's really one of two surviving heirs of a tycoon who has the right to inherit his mass fortune when she turns 18 in half a year. Fubuki, a young and beautiful maid, and Kogarashi, a big burly maid guy with a mask, have been assigned to keep Naeka and her brother Kousuke safe from those who would plot their demise, and to steal the fortune she would inherit.

(Source: AniDB)