text: Plot Ten years ago before the events of the series, a spatial anomaly which became known as "Heaven's Gate" appeared in South America. It was followed by the opening of "Hell's Gate" in Tokyo, altering the sky and wreaking havoc on the landscape. At that time, "Contractors", people with special abilities, capable of supernatural feats, emerged. Kept secret from the public, Contractors murder in cold blood and block their emotions with logic and reason. Their abilities are acquired at the cost of their humanity, and their name derives from the requirement to "pay the price" each time their powers are used. Nations and organizations around the world train and use Contractors as spies and assassins, resulting in violent battles for valuable objects and information.
  After the 'Heaven's War', the United States loses its position as a superpower to a mysterious organization known as the Syndicate. Darker Than Black follows a Chinese Contractor code-named "Hei" as he undertakes espionage and assassination missions in Tokyo directed by the Syndicate. In his false civilian life, where he is known as shy a student under the alias Li Shenshun, Hei is assisted by Yin, an artificial human known as Doll and Mao, a Contractor trapped in a cat's body and overseen by former police officer Huang. The series has a villain-of-the-week format, with a variety of characters such as a Japanese Public Security Bureau who oversee the activities of dangerous people with supernatural powers.