Majin Tantei Nougami Neuro
Matsui Yuusei
Shueisha (Japan)

Majin Tantei Nougami Neuro (Manga)Edit

A demon, Nougami Neuro, who feeds on mysteries, has come to the human world after eating all the mysteries in his. But as a demon, he can't act overtly. The first thing he does is force a high school girl to become a detective, while Neuro acts as her assistant.