Directed by Tensai Okamura and animated by Bones, this is a neo-noir sci-fi anime.

Ten years ago, a strange structure called Hell's Gate appeared in Tokyo. Its existence replaced the real sky with a fake sky. At the same time, people with strange powers called Contractors started to appear. Every power has a cost, called a Remuneration. The Remuneration takes many forms, including eating dandelions, earmarking the pages of a book, or humming a tune. Also, every contractor has a corresponding star in the fake sky.

The story centers on Hei, a very powerful contractor who can manipulate electricity. He works for an unnamed organization and fights other contractors to carry out his missions. In public, he assumes the identity of Lee Shenshung, a softspoken Chinese college student.

The official website is here: http://www.d-black.net/

EDIT: Potential spoiler links removed (thanks for the heads-up Kero).

Worst thing you can do to any person who did not watch an anime is point to wikipedia. Spoilers everywhere (I didn't see this particular article though, but I don't even try) =p