I've seen this a few times. I don't remember the name but I know there's one in particular centered on this, where the hero is obsessed with visual novels and such and when his favorite new VN suddenly reveals that his favorite heroine had another boyfriend before the PC he flew into a rage at the very idea of having any interest in someone who's no longer a virgin; he ends up pursued romantically by a Gal (I don't know if she's a virgin, didn't make it that far). Sadly, this opinion is so big that it seems there are even people that'd reject rape victims as "used goods" (this's part of the reason it's so common to find a girl who was forced into slavery or prostitution somehow kept her virginity despite the situation).

As such, I have two primary requirements. First, the guy has to be firmly opposed to the idea of dating a girl who's no longer "pure", regardless of how far he takes it or what acts, consensual or not, he feels make one "impure". Second, obviously, he ends up falling in love with an "impure" girl.