Matantei Loki

Loki, the Norse god of mischief, has been exiled to the human world for what apparently was a bad joke. Along with being exiled, he's forced to take the form of a child. He's told the only way he can get back to the world of the gods is if he can collect auras of evil that take over human hearts, to do this he runs a detective agency. However, at some point other Norse gods begin to appear with the intent to assassinate him for reasons unclear.

(Source: Anime News Network)

Note: Volume 6 includes the side story "Ore wa Dokushin Kizoku (俺は独身貴族)"