えねま2

Ema is a student council president, nominated by former student council and her very close friend president Seira. Main heroine Shibuki together other council members Ema and and Kimidori sets to explore the old school building to uncover the school ghost legend. There girls fall down through the rotten floor and appear in a room with unusual drawings. There they have strange visions and develop new experiences as a result. The next day an angel appears before Shibuki. The angel claims that the world is in huge danger - sex demon starts to possess humans. In order to prevent possession the belly should be cleaned from all the poop. And that task is mounted on the shoulders of Shibuki.

[From vndbreview]