Kuro no Tantei Black Detective

Synopsis

Kuroba You is a sadistic detective who enjoys nothing more than destroying his targets emotionally and psychologically through his deductive reasoning. Toiro Arata is a naive and slightly masochistic boy who gets duped by You into becoming his assistant, or slave. These two team up to become the "Black & White" detective, solving crimes and chasing after criminals. (Source: MangaHelpers)