Honestly, after all the tomfoolery this guy has gotten up to he can't be angry at his crush for having some fun of her own. Although, I'm guessing she's probably already ntr'd + mindbroken when she gets her memories back.
Well she could've raped him while he was sleeping in the hospital bed, in the "real" world... But yeah this purity shit in Japanese culture is pathetic.
@Bakaman - Japan pretty well invented the incel culture, they've just never had a name for it, lol. But yeah...the whole 'purity' thing is usually something thought of by young people who don't know any better. Noone who's ever had sex (and didn't have to like, pay for it out of desperation) would actually give a fuck if their partner wasn't 'pure' or whatever...it's really dumb and shows that the writer or mangaka is a closet incel.
It's more jealousy and less purity. He's already thinking of her as his woman. What man can sit still with the idea of some other guy fucking his woman?