From Dan of Population GO:
Three friends, Kotori, Yuuto, and Rin are trapped in school when the principal halfheartedly summons a horde of demons. The demons make a pact with each student in exchange for possessing them. Most of the students wished to be be good looking or to have longer legs, but Yuuto manages to stave off the possessed student body while Rin overpowers the weak demon possessing her. Yuuto makes a pact with a demon to return the school to normal, but what will happen to the school now that each student is being possessed by a demon?