text: Original video animation A four-episode original video animation (OVA), , was included on the second, fourth, sixth and eighth collected Blu-ray and DVD sets of Darker than Black: Gemini of the Meteor released from January 27 to July 21, 2010. The OVAs are set in the time between the two seasons. Hei and Yin have left Tokyo and are on the run from the Syndicate. They are attacked by Contractors, and Hei notices Yin's alter ego Izanami (who would bring about the end of the world). Yin asks Hei to kill her; the Contractor cannot, and they are caught up in an explosion. Hei becomes depressed after Yin's apparent death; a CIA agent tells him that Yin is still alive, setting up the events of Gemini of Meteor. The closing theme is "Darker Than Black" by Yasushi Ishii. For the English-language release, the OVAs were included in the Gemini of the Meteor compilation.
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  A manga adaptation, illustrated by Nokiya, was serialized in Kadokawa Shoten's shōjo manga magazine Monthly Asuka from March 24 to November 24, 2007. Its chapters were collected in two  volumes, released on August 23, 2007, and January 24, 2008, respectively. The series was licensed for English release in North America by Yen Press, which released both volumes in an omnibus edition on June 15, 2010.
  A second manga adaptation,  illustrated by Yuji Iwahara, the anime series' character designer, was serialized in Square Enix's seinen manga magazine Young Gangan from May 15, 2009, to January 21, 2011. The manga is set one year after the events of season one, and focuses on Hei on a mission to stop one Contractor from giving civilians the chance to become like him. Square Enix collected its chapters in four  volumes, which were released from October 24, 2009, to March 25, 2011.