Lesson of the Evil
It left me confused and disturbed as hell, but I guess that was what the movie was going for.
"High school teacher Hasumi Seiji is the most popular teacher at his school with an attractive smile. Yet, Hasumi Seiji is a psychopath. To solve some of his school's problems, like bullying, and to protect himself, Seiji begins to kill his students one by one." - mydramalist
I rate it 8 out of 10 and would recommend it to anyone who liked 'Confessions', although 'Lesson of the Evil' wasn't as good.