Manga Name Hunt - Help please?

[KouhaiZane]

I have been looking for a manga, don't know the name of it unfortunately. It involves a graveyard/shrine of demons that is sealed with in a part of a "old school" a guy and a girl uncover and set them all free, one stays there and toys with the two of them. The demon smacks the boy(guy) into the shrine and there is some guardian demon there and it talks to him. Tells him that if he wants to save himself and the girl to give up his body... Well he agrees and becomes a.. "..." That is what the name of the manga is.. (i think) the dog guardian hides as his jacket. and his job is now to hunt down those demons who have ran away.

If anyone has any information regarding this manga please let me know I will be highly thankful!