When Havoc is found, it is revealed that she has lost her supernatural abilities—becoming a "Regressor"—and is now a shell of her former self, plagued by the memories of her past actions. Series Context: Darker Than Black

Individuals who gained powers but must pay a "remuneration" (a repetitive or strange task) every time they use their abilities.

The series is set in a near-future Tokyo where a mysterious territory known as appeared ten years prior.

The protagonist, Hei (the Black Reaper), is tasked by the Syndicate to retrieve Havoc before other agencies can reach her.

Various international intelligence agencies are desperate to capture Havoc to uncover the secrets of the Gates.