Koakuma Kyoushi♡Psycho

A captivating new teacher, Kasai-sensei, arrives at a problem classroom. The previous teacher had been hospitalized for a suicide attempt due to student bullying. "My goal as a teacher is to bring joy to my students," Kasai-sensei says with a laugh, when the bullies start harassing her. However, the students do not yet know her true nature: Kasai-sensei is a psychopath...!? (Source: Bunkasha, translated)