in the anime any kind of erotic material and the saying(and by extension the doing of in certain ways) of indecent things is 100% outlawed. This actually leads to ultra thirst girls development. A lot of the students in the school have absolutely no sexual knowledge or desire. She starts out like them but an accidental kiss activates her sexuallity and puts it in overdrive making her a max level sex crazed yandere, but she doesn't understands what she's doing, she just knows it feels good

well it is illegal in his world.