Kyou no Cerberus

As a young boy, Chiaki Mikado had an encounter with an unusual, three-headed puppy, and as a consequence of a bite from that dog, he lost a piece of his soul. Now a teenager, he finds himself unable to enjoy anything, but the three-headed dog is back in human form (or more accurately forms) to fix all that!

Turns out that the three heads of the mythical guardian to the gates of the underworld are actually unique individuals, and each a pretty young girl at that! With his new roommate(s) leading the charge, can Chiaki experience the happiness that has so long eluded him?

(Source: Yen Press)