Darker than Black: Kuro no Keiyakusha Gaiden
Darker than BLACK -黒の契約者 外伝
After the incidents in Tokyo, Hei and Yin try to bury their past and start a new life, but everywhere they go someone seems to be following them. Unaware to Hei, Yin's current odd behavior appears to be related to a prophecy that might lead to the end of the world.
(Source: Anime News Network)