Danganronpa Gaiden: Killer Killer

In response to The Biggest, Most Awful, Most Tragic Event in Human History, an organization called Future Foundation was created to combat the chaos still present even after the death of The Mastermind. Misaki Asano is a new recruit, working as a special investigator for the 6th Division's Special Case Bureau—a branch dedicated to only the most bizarre and challenging murder cases. Alongside her partner, Takumi Hijirihara, they aim to combat despair one case at a time.

Though, perhaps their most challenging case is that of the mysterious Killer Killer, a bizarre serial killer who chooses to target other murderers.

(Source: Danganronpa Wiki)