If you liked the Hakushi no Fukakai na Yaen manga, the Anime-Planet community thinks you'd like:
In Victorian England it is commonplace for the rich and wealthy to have a staff, led by a head butler, to run their households; the Phantomhive Estate is no different. The young and demanding Count Ciel Phantomhive, child owner of a toy company, lives in the grand countryside manor. Sebastian is his head butler, and the epitome of perfection; he effortlessly and gracefully completes his day-to day chores and fixes the countless mistakes of the other employees. However, whilst on the outside all seems prim and proper, a more sinister secret lies just beneath the surface. Sebastian is in fact a demon bound by a contract with the young count; he will loyally serve and fight for him in return for his soul.