I know the concept exists, but to my knowledge nobody has written a game with it. At best there might be a single scene of a girl watching that quickly turns into threesome. I've never seen something where the girl is like the redhead, tied up and fully denied sex only able to watch as her partner goes at it with another girl. In other words I'd like to see Mike's Cuckolding Report some day.
Yes, one can write a good story with interesting characters that plays out like it should, however, capturing the mindset is another story entirely. There is a reason why writers are paid the big bucks and even then not every story is a hit. Writing is hard for a professional with years of experience, you either need an education or have to be a prodigy when it comes to the do's and don'ts of writing and some of the more highly rated VNs on this site are full of rookie mistakes(I took creative writing classes in college because I needed the elective credits). The stars would need to align perfectly in order to pull off what you're suggesting, and while it is technically possible, the odds aren't stacked in its favor.
I tend to assume that if something has NTR in it then it was written by an NTR fan, because if you think about it, NTR doesn't make a whole lot of sense. After all, if a romance fails then she just breaks up with you or you don't get together. It makes no logical sense for a woman to fall in love with a guy but then change her mind at the first sign of trouble and begin cheating on him, however to an NTR fan, this scenario makes perfect sense.
