Tokubetsu Jugyou 3 SLG The Animation.

Based on a game by Bishop. Ishizuka Kengo has started working as a teacher at the school he graduated from and has been given the job of taking care of the old school building until it gets demolished. While for others that task may have been troublesome for him it is an opportunity to satisfy his dark desires, and he wastes no time doing so... Ishizuka's first target is Morimiya Saki, a student at the school, but soon he also targets Saki's friend Arisa, Saki's mother Rie, and another teacher at the school—Mashima Mikako. What awaits these four at the hands of the sadistic teacher?