Or the girl instantly becomes a slut at day 1
I've been meaning to ask, is there any Mystery NTR game with this premise? A male MC game where the female LI/heroine is actually a full-on casual adulterer behind the scenes from day 1 (also perhaps through day negative something, meaning she was that way before the game's story even took place), and the MC is none the wiser up until he finally learns all about it restrospectively?
Maybe this is a weird request, but i always largely dislike the corruption element of the typical Netorare plots, since i usually will either find the male villain's mannerisms unbearably cringeworthy, or would end up deeply pitying the heroine. I'd prefer a plot where a by-default debacuhed couple's pretentious romance crash and burn due to the girl's clearly self-initiated clandestine adulterous escapades being unveiled/getting out of hand. I want to see the male MC being extensively lied to by the two-faced heroine, who just casually go behind his back. Not outright Netorase tho, since i want to see the male MC being distraught. I guess i don't mind if there is a (lousy) netorase ending or something.
The only game i know (from the not-so-many i played) whose storyline best (albeit still only loosely) fits the bill is the now-abandoned Girlfriend Tapes by BootyProfessor.
Bonus points if male MC is a semi-unlikeable wannabe womanizer, and the female LI/heroine is twisted enough to never show any semblance of guilt.
EDIT: more bonus points if the affairs involve multiple casual partners and a plethora of mix n match group encounters. Not a boring "suddenly monogamous to Mr. Alpha" schtick. Maybe with elements of the female peers being "in on it" mixed in. The full package.
Also, no marriage/divorce element if possible. Despite my seemingly dark fantasies, i actually respect the sanctity of marriage.