Saya Akabane  

, 赤羽 沙矢

Ayas elder sister has a gentle demeanor but secretly enjoys inflicting pain and causing harm to others. She partners with the equally sadistic school nurse, Oku Kaname, who shares her love for cruelty. There is often a running joke that Saya cares more about Oku than her younger sister Aya, and both she and Oku frequently tease and bully Aya, making her fearful whenever they are together. It's also suggested that the two of them may be romantically involved.