Satsuriku no Tenshi

Rachel Gardner awakens in the basement of an unknown building with no understanding of how she arrived or why parts of her memory are missing. Searching for an exit brings her face to face with Zack, a bandaged serial killer carrying a huge scythe who initially hunts her. Rachel's wish to die changes the encounter: she asks him to kill her, and he agrees on the condition that she first helps him escape.

The pair climbs floor by floor, each level controlled by a dangerous person with a new trap or trial. Strangely, the building's inhabitants know more about Rachel than she knows about herself. Every step upward exposes pieces of her past and the reason she was placed there, while the absurd promise between a girl seeking death and a killer seeking freedom becomes the bond both rely on to survive.