Harakuro Shiro to Nora no Kuro

Hiro ran away from the countryside for the sake of finding a better life. Unable to find a job, he ends up on the streets like a stray black cat. Then, to his surprise, he is picked up by an "angel." However, this "angel" named Kai may be more like a devil than he expected.

(Source: Exiled Rebels Scanlations)