Satsujin Gokko

Fujisaki Miki is a first year student whose obsession with murder frightens many of her peers. Student Council President Aoi takes it upon herself to scold Miki and set her right. But instead, Aoi is drawn into an increasingly elaborate game of "pretend-murder" with Miki that threatens her social status at school, and awakens new feelings deep within her.

https://yurinavi.com/2018/01/14/satsujingokko/