It was broadcasted in Japan from April 5, 2007 to September 28, 2007. The music for the series is composed by Kanno Yoko (菅野よう子) (remember she appearing on Sakamoto Maaya's video that I showed you? Watch it here!). The series has also been adapted into two manga series, which are serialized in Monthly Asuka and in Young Gangan. The anime also was awarded Best Original Anime of The Year by GoGoplex, a popular magazine for teens.
Ten years ago, a mysterious spacial anomaly known as "Hell's Gate" appeared in Tokyo, altering the sky and wreaking havoc on the landscape. The real stars disappeared, replaced by false stars. During this time, people possessing various special abilities emerged, each capable of different supernatural feats - these are known as Contractors. Each Contractor has a corresponding fake star, which reacts to their activities. As such, Contractors are usually identified by their star's Messier catalogue number.
Kept secret from the masses, these individuals are known to murder in cold blood, smothering unnecessary emotions with logic and rationale. Their incredible abilities, however, are gained at the cost of their humanity - Contractors are thus named because of an involuntary compulsion to "pay the price" each time their power is used, which can range from eating particular foods and completing meaningless tasks, to self-harm and changing their bodies in peculiar ways. Various nations and organizations around the world train and utilize Contractors as spies and assassins, resulting in violent battles for valuable objects and information.
Following the disastrous Heaven's War, the United States lost its dominant position as a superpower to a mysterious organization named the Syndicate. The story revolves around a Chinese contractor codenamed "Hei" as he undertakes various espionage and assassination missions in Tokyo under the direction of the aforementioned Syndicate.
A sequel entitled Darker than Black: Gemini of the Meteor (流星の双子(ジェミニ), Ryuusei no Jemini) premiered in Japan on October 8, 2009 and ended in December 24, 2009.
Also, each one of the two seasons was followed by OVAs to fill some unexplored topics in the plot.
I think it is an awesome anime, and I think you can easily like it, because it's really cool. But no more waits! Have a look at the trailer below!