Kitsune No Akuma To Kuroi Madousho. Follow the story of Kyuuki, a strong, proud fox demon who's just awoken recently. Kyuuki needs a host, and normally she'll need the high school student, Kamishiro Shin, if it weren't for "his ability", and for the fact that he got hold of the black Grimoire which controls his existence. Shin, as long as he's alive, is bound to the book. Therefore, he can't break his bond with Kyuuki; even those who wants the power of the book are going to come after his hide regardless of time and place.