Tomoya

A man who has lost his memory and has no idea why he even is at St. Emilia Girls Academy. He is also an orphan. Despite his current situation, Tomoya doesn't try to be pessimistic and just lets the days roll by while working.
He is a member of the prostitute circle. His main job is to make the girls "bloom" (sexually train them), who then get sold as mistresses to wealthy men.
In order to hide the fact that he's a man, he cross-dresses and calls himself "Sister Yoriko."