Kono Youchien wa Kurutteiru.
この幼稚園は狂っている。
My library
Description
The onigiri was stuffed with hidden razor blades… On my very first day on the job, I watched another teacher spit blood out of her mouth, her face twisted with pain. I can't be the only one who thinks this is beyond messed up, so why does everyone else look so happy? Source: Manga Planet