Black Butler
Sebastian and Ciel.

Black Butler (Kuroshitsuji in Japanese), is a shounen マンガ and companion アニメ series (although it's pretty obviously looking for a crossover shoujo audience). Originally created によって Toboso Yana.

The Phantomhive family is a respected and distinguished house in Victorian London. Despite a mysterious 火災, 火 killing off the 前 lord and lady Phantomhive, their 12-year old son, Ciel Phantomhive, has managed to both build a massive toy and キャンディー company within 3 years, as well as serve the クイーン as a major contributor to England's black-ops.

It really, really helps that Ciel made a literal Deal With The Devil to acquire a super butler: one Sebastian Michaelis, capable of dispatching The Mafia または other threats (including those of the スーパーナチュラル variety) and then bake the perfect pastry. He has agreed to aid Ciel in all of his endeavors until Ciel "succeeds in all of his tasks". Then Ciel's soul belongs to him.

So Ciel leads a double-life, his service to the クイーン combined with his own dark スーパーナチュラル dealings, and maintaining the peace of the Phantomhive Mansion and its less than serious staff.

Mix and stir Hellsing and Count Cain with Loveless, at least toward the beginning. No, seriously.