Nijou Shizue

She is the headmistress of the prestigious Jinguu Academy
She was a mentor of the protagonist when he was a student, and she brought him in to help him solve this situation.
She does not tell the confused protagonist much about her intentions or thoughts.
She ordered her students to have sex with the protagonist in order to save the school.
She herself liberates the protagonist's morals with her own body.

As a means of countering the strange phenomena that attack the school she uses various magical arts.