沼中　大吾

The English teacher at St. Estella Academy. 

Despite his polite manner of speech, he is widely perceived by the students and other teaching staff as completely lacking in dignity; as a consequence the students in Yukito's class are free to disrupt his lessons as a form of stress relief without any repercussions.

 The facade he puts up in the main school building is a completely different one from his true nature as the abusive and exploitative tyrant of the C-class block. In addition to taking revenge on students who disrespected him in the main building (via physical abuse or sexual violation in the case of female students), he is also tasked by Yanagi to dispose of the suspected witches forcibly removed to the C-class building for experimentation.

His greatest pleasure is the deflowering of virgin students in the C-block. He quickly loses interest in violating students he has deflowered, dismissing them as "second-hand". /