Nightmare Fuel / Hell Teacher Nube

Hell Teacher Nube usually mixes horror and Japanese folklore with lots of comedy, but several episodes are more disturbing than funny, especially for a Shōnen manga aimed at teens and pre-teens, where (save for the teachers) all the protagonists are in fifth grade.

Spoilers below.


http://tvtropes.org/pmwiki/pmwiki.php/NightmareFuel/HellTeacherNube