Boogiepop

The shinigami whispered of among the female students of Shinyo Academy, few people know that Boogiepop actually exists. Normally dormant, Boogiepop rises to the surface when enemies of the world appear. Boogiepop's appearance and voice are ambiguous: they seem both masculine and feminine at the same time. However, hidden beneath their signature black cloak and black, pipe-shaped hat, little is ever seen of them. Straight-faced and to the point, Boogiepop acts as mechanical as they claim to be. Boogiepop speaks in an archaic manner, and seems fond of whistling the overture to Wagner's Die Meistersinger von Nürnberg.

(Source: Wikipedia)