Zerozaki Soushiki no Ningen Shiken

Iori is a high school student with no idea what she wants from the future, and she tends to run away from her problems. On her way to school, strange, dead-eyed people attack her, but a mysterious long-haired man saves her. Later, her friend Jion appears to fall under the same murderous influence, and Iori discovers that she can defend herself against his violent attack. The man from that morning introduces himself as Zerozaki Soushiki and asks Iori to become his little sister. As her life takes an unexpected turn, Iori must face what she has become involved in and whether she can survive the change.