Maou no Keifu

In the Maou no Keifu series:

1) Nemureru Maou
2) Maou no Musuko
3) Mahou no Meiyaku

Touya Takatsukasa was kidnapped and brutally raped as a twelve year old, only to have all his captors viciously murdered around him. That was also the start of his father coming into his room at night. It's six years later and Touya has never left his home again, but even he's heard the rumors of how his father made a pact with a demon for wealth and power. Now that's he's of age his father has decided it's time for him to leave the house, and assigned him a bodyguard, the oddly devoted Kuroha Kazuomi.

(Source: MU)