The biology teacher at St. Estella Academy whose remit includes the students in A-class.
His emotionless, machine-like demeanour is reflected in his teaching style. His ability to remain calm and detached whatever the situation unnerves students who keep a respectful distance.
<hidden by spoiler settings> Some time after Maya Kisashi took over as school director, Yanagi arrived at the school claiming he could help with the witch phenomenon. Taking advantage of the director's desperation, he was granted carte blanche to investigate students suspected of becoming witches and had limited access to the school's funds to expedite his experiments as well as fix any unwanted problems arising from dead students. By the time Yukito enrols at the academy, Yanagi has experimented on and raped countless female students with his sole success in returning a student to normal being Muroyama Kazuko. Most if not all of the books regarding the witch phenomenon in the academy locality have been monopolised by Yanagi for personal reference. Yanagi's true aim in conducting the experiments is to open a path to the source of the witches' powers as he hopes to obtain power and immortality from the gate directly (since witches can only be female)
Yanagi sees the students suspected of being witches as nothing more than guinea pigs for his experiments, hence his instructions to Numanaka and Kajiyama to dispose of them as they see fit once they no longer serve his purpose.