Souin Ningyou ~Obieru Shoujo-tachi~

Main character was sorry for classmates bullied at former school, so in this new school he decides not to allow it. His former bullied classmate Marie transfers soon as well, but the victim starts to act like a bully for another girl this place. Protagonist arranges a seminar for both girls, but at some time he starts to violate them for his own pleasure.

[From vndbreview]