Hametsu no Kanojo

Hametsu no Kanojo summary:

Reiko, Kazu and Yukari are three childhood friends with a good relationship. Reiko, the self-proclaimed older sister of the group, tells herself that they are like family, and throws away  her love for Kazu. As for Yukari, she also has feelings for Kazu. Thus, one day, the relationship between the three begins its gradual descent into madness... A shocking psycho-love story between young people begins!!