Angels of Death [TV]

A girl named Rachel wakes up in an unknown place with no memory of how she got there or what her life was. She starts to explore the area and ends of finding a bunch of psychopathic people that each have their own floor in the building that their in. She ends up befriending a serial killer named Zak who at first wanted to kill her but soon lost interest because of the loss of her emotions. None of the Psychopaths are allowed to leave their floors or they are free to be killed by the other psychopaths based on the floor that they stop at. Rachel and Zak both partner up. Rachel wants to find out who she really is and Zak wants to escape.

Similar in these categories.

Death Note

Hellsing Ultimate

Kuroshitsuji

Koutetsujou no Kabaneri