Alice no 100°CC

Aoi Kururi is an onmyou-ji who is studying smells at a private academy. He in fact hates using onmyou magic, but when a spell is mysteriously cast on his whole class that causes everyone to wet themselves, he finds that with the warm power and sweet smell of girls' pee, his magic becomes more powerful, and he saves his class by breaking the spell. This is the story of the strange misadventures of Aoi, his sisters, and his friends.

(Source: MangaUpdates)