Mahou to H no Kankei.

Private Academy hosts a number of fancy departments with 30% of the cultural ones researching magic.
Main character is the secretary of a student council there. He is asked not to demote understaffed departments into clubs due to importance of their research. One such small department studies the connection between magic and sex. Three brave girls are chosen as test subjects and protagonist as a moderator.

[From vndbreview]