Misaki Asano is a new recruit, working as a special investigator for the 6th Division's Special Case Criminal Investigation Unit, a bureau dedicated to solving the most bizarre and challenging murder cases. Alongside her partner, Takumi Hijirihara, they aim to combat despair one case at a time. Their most challenging case is that of the mysterious Killer Killer, a bizarre serial killer who targets other murderers.
The mask of Sparkling Justice, a serial killer mentioned in Danganronpa 2: Goodbye Despair, is on display in Eiichirō Saiyama's room in Chapter 3. Because the identity of Sparkling Justice is unknown, it is possible that Sparkling Justice and Killer Killer may be the same person, as they both have the same M.O. (murdering other killers), which is supported by the fact that the name of Sparkling Justice in the original Japanese release of Danganronpa 2 is Kirakira Seigi (キラキラセギ). It is unknown if this is intentional or simply a reference.