DISSOLVING CLASSROOM (Yokai Kyoushitsu), by Junji Ito. First published in 2013 and first published in North America in 2017.
PLOT:
Across Japan, a strange phenomenon is happening. People are having their brains melted out of their very heads. Sometimes their entire bodies disappear into a puddle of goo, leaving nothing but a stain. Others have their faces warped into hideous visages, all while telling themselves that they are unparalleled beauties. All of these strange occurences seemed to be tied to two people: Chizumi Azawa, a creepy girl with a fondness for brains, and her big brother Yuuma who can't stop apologizing for everything.
