This poor childhood friend, unaware of the amount of BS he goes to save her and the world and then having watch herself getting NTR'd by what she thinks is incest...
@Tamerlane NTR kind implies she already staked a claim to him in at least some fashion beyond "we're friends." If we wanted to be even more strict you can't really get NTR'd if you're a woman to begin with, cuckolding is gender specific for some reason.