Seeking ntr with a nice guy - good girl couple, painful betrayal, guilt, fragility, almost masochistic suffering

[nscrty]

Gradual nuanced corruption, no blackmail, and the predator is in the position of power, smart, or just a cunning womanizer not a creepy uncle or landlord

Would be great to see many moments with suggestive jokes, where a girl holds back her laughter in front of a guy or boyfriend is laughed at behind his back, or he's mentioned during sex in a derogatory way
For example Turning the Page has a lot of chatter, but not enough innuendo

 

[FrankWestPhoJrn]

+1

 

[Ligvan]

+1

 

[Pretentious Goblin]

https://f95zone.to/threads/henteria-chronicles-ch-2-the-law-of-the-tribe-update-16-n_taii.61811/
Though as much as I like the game, admittedly the way the main LI starts being corrupted is arguably one of the weakest parts of the writing. Still, I recommend it for NTR of a genuinely nice couple of people (I think they're not officially an item though). The sequel should be good too.

https://f95zone.to/threads/shadows-of-desire-v0-4b-shamantr.171123/
This one is almost the opposite. Much rougher writing, especially at the start of the game, and a more aggressive approach to corruption. But it has the "behind the BF's back" type content for sure. It has three routes: cheating, cuckold and blackmail, and you should follow the guide to get the one you want. I wouldn't recommend it for corruption though, it's a pretty gonzo and tongue-in-cheek game.