Zone-00

Kujou Saburou is an ordinary high-schooler, hyperactive and strangely interested in mysterious (alien) things. He quickly becomes friends with a new transfer student, Shima Ango, who happens to find him in a game of hide-and-seek. But what he doesn't know is Shima's true goal: the extermination of mononoke terrorizing the Toyko area. Caught in the middle of their fight, Kujou loses his head, unsealing an Oni inside of him...

(Source: Bliss)