Lesson of the Evil is a horror thriller movie about a high school teacher who turns into a psychotic killer and carries out a brutal massacre. Set in Japan, the movie explores themes of atrocities, teenage girl's life, and the dark side of the education system. The teacher uses text messages, sexual blackmail, and violence to manipulate and terrorize his students. The movie is based on a novel and depicts the twisted mind of the killer as he plans and executes his destructive acts.