Kiss x 400 Natsukashiki Hibi no Renzoku

Main character lacks contacts with women. He belongs to a certain university circle with a vague purpose. One day, a female student from the same circle asks him about the first kiss, but he does not remember anything like that. Different girls start to approach him with questions about past relations, but he is unaware of that either. So girls decide to have sex with him and awaken those memories. Is it really possible to get memory back this way?

[From vndbreview]