I reread the last 2 novel chapters of Locked Room. The humor is definitely in the novel. And as I thought, the anime super-changed the story's end. The teacher isn't a serial killer like in the anime. He was someone who freaked out when his lover (the student) claimed she was pregnant in order to keep him tied to her. There was no fire either. The mangas were closer to the novel in how the plot ended than the anime.