Kimi ni Semaru Otome no Lesson

Yasuto, the protagonist, is eager to find a girlfriend and have sex, but at the same time he is quite the idealist who wants a romantic, pure relation.

One day when coming back home after refusing to join a blind date his friends organise, he finds a girl in his room. The girl tells him that he has been randomly chosen to transfer into a private all-girls school for ladies in order to help them get accustomed to boys and love, as a countermeasure against low-birth rates.