Darker than Black: Gaiden is a Japanese original video animation (OVA) series created by studio Bones and directed by Tensai Okamura. It is a sidesequel to the anime television series Darker than Black and a prequel to Darker than Black: Gemini of the Meteor. It consists of four episodes about the main character Hei and his partner Yin, with the events taking place between both seasons. After betraying the Syndicate organization, Hei and Yin escape from Japan to live a peaceful life, but Yin later develops a god-like alter ego that causes mayhem.

Tensai Okamura , born Yutaka Okamura on December 13, 1961, in Fukushima Prefecture, is a Japanese anime director and animator. Okamura grew up in Yokohama, Kanagawa Prefecture. He is a graduate of Waseda University's department of science and engineering. In 1991, he changed his first name to Tensai.