(Source - Wiki)

Plot Summary: In Tokyo, an impenetrable field known as "Hell's Gate" appeared ten years ago. At the same time, psychics who wield paranormal powers at the cost of their conscience also emerged. Hei is one of the most powerful of these psychic agents, and along with his blind associate, Yin, works for one of the many rival agencies vying to unlock the mysteries of Hell's Gate.
List of Characters
Genres: adventure, drama, mystery, science fiction, supernatural
Themes: neo-noir, post-apocalyptic, superhuman, superpowers
Episodes: 25
Age Rating: Older Teen (Significant bloody violence and/or swearing and/or nudity)
(Source - ANN)
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darker than black is hard to explain. its a modern day fantasy/crime/gore series. it moves very episodically and most of the time it feels like its just an experimental anime, but with a stroy line that is only really uncovered at episode 5 it still keeps a good pace with interesting characters and eventually revealed plot lines. btw if your squeemish then DO NOT WATCH THIS.
the main character is chinese student Lee Shenshung. he seems shy and bland but when it calls he pulls out his alter ego Hei the black contractor or as the police call him the BK-201. he is what they call a contractor. a contractor is a person who is given a power in exchange for something like self harming. in the first episode a contractor is seen snapping his fingers in contract. Hei i don't know what he does but he still is a contractor. the modern day idea of tokyo in the anime is hiddwn by a fake sky line and a huge building called hells gate which circles off the city perimiter. the people occupying it are from a company named pandora and they experiment with contractors. i don't knwo what spectres are but i'm guessing they're the stars. oh and another thing: a star falls when a contractor dies. darker than black is an enthraling series that captures the imagination with good characters, a strange back story, lavish drawings and even a great sound track. oh and above all: its made by aniplex and bones. keep a look out for references to either companies in the anime itself. be prepared. this is gruesome stuff.