If you're playing this for NTR, there's only one thing I can tell you… don't.
The NTR is a very minor route, which in my opinion doesn't even count as real NTR since you're not involved with the girl. She doesn't do it for the love of the game either. It's just basic blackmail. After that, it turns more into a sharing thing since you actually get to decide who she fucks. So again, if you're playing for NTR, don't.
But if you're here for story, lore, hype, and some freaky shii, then welcome aboard.
Not really the case, the mc has made it pretty clear he pined for this girl all his life. He confessed to her and she rejected him. Saying it "doesn't count" because he wasn't in an official labeled relationship is kinda ridiculous.
Anyway on subject in his past she slept with a dozen+ guys, even offered to sleep with the mc out of pity, which he rejected. So all things considered the mc was ntrd pretty much all throughout his teenage years up to the start of the game. I'm pretty sure he created this character with the sole design idea of adding ntr, and also making an optional romance route just for the sake of those who don't like it.
He actually did various surveys about what his audience wanted, here's one I found a while back.
She had two ntr routes if I recall correctly, one where it was mostly rapeblackmail and drugs, the other where she was coerced but overall pretty ok with it. I'm pretty sure he was planning a larger expansion until he realized how unpopular the genre was. Course, that's just a guess.
Having said all that, you're correct on one thing, that it's mostly an incredibly small portion of the game fairly easy to avoid.
