Like I said I don't think it's difficult to write a reverse ntr story where the guy is stolen, corrupted or manipulated by some other girl. A simple one would be that both a guy and a girl have been together since they were kids and when they turned adults, they about to get married, lost their virginity to each other on their wedding night and then some other girl comes in who is more sexy and curvy than the longtime girlfriend.
Example having bigger boobs where the male partner can titjob her and the longtime girlfriend don't have the assets for that. Wouldn't the long time girlfriend feel jealously and get humiliated from that the thought she don't have the assets the new girl has and is forced to watch it happen and cry over it.
After I got the new terms I did some searching and I was able to find these two that best what I described and in both of them the female partner was devastated, jealous and humiliated seeing it and it doesn't take anything away or make it any less appealing than the male ones.
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If I was able to find these then there is defiantly more, it just sounds like ntr is heavily one sided against men like a gender bias or favoritism, or people are just unwilling to make ones against females to balance the scales and Equal the Genders.