Demon from Afar, Vol. 2 by Kaori Yuki

From the ultimate nightmare that is Walpurgis Night, Sorath escapes to modern Japan. There, he lives in an unconventional household that includes Nonoha, the daughter of his dearest friend, and Mephistopheles, the Duke of Hell, who bides his time for a chance to kill his master. This time, these hands will protect my loved ones-- That's Sorath's wish, but somehow Nonoha is slipping through his fingers. Will Sorath's hands once again be stained by the blood of the person he cherishes most?