The idea for Darker Than Black came to Okamura while he was creating the anime Wolf's Rain, and was based on his handling of protagonists.

[1] The bi episodic structure is based on the experience Okamura worked as storyboarder in the anime Cowboy Bebop.

The second half, since this original show needs to be put into an end, it is Shotaro Suga handling the role as his first time to be series composition.

[4] Darker than Black: Gaiden first envisioned when Bones decided to create the series' sequel.

In contrast to the new style and content from the sequel aimed towards new viewers, the 4 OVAs were made for the returning fans who want see what happened after the first series.