In modern day Japan when humans and demons co-exist a low life indebted, but strong wolf demon Kazuma is forced into a contract with a smart ass girly boy named Hiro. Hiro who lives in, because of his weak state of going through an unknown illness, lives and owns a hospital. He gives Kazuma a chance to pay off his debts by working with him on finding and catching demons that go out of control throughout the city. Although when their paths inter twine with each other they are both putting their lives at risk for their pasts' are not friendly ones. After Kazuma slowly grows extremely close to the annoying and troublesome Hiro he suddenly meets his supposed to be dead girlfriend Kannako. Will Kazuma leave Hiro to struggle on his own to get the job done or will the jealous and determined Kannako do it for him as she tells him " I will do anything to have you back. Even if I must kill for it".