Allow me to assist! Hold Left bumper to call an assist hero!
"We are Venom!" *Action start* what leads to NTR that people forget as a mechanic is letting Relantionship to drop below a certain point (5 if i recall when it turns red) At which point yes NTR will happen to the character in question. For instance! Alexis, She's Loyal to the MC off the bat, so unless you try (or turn on hardmode which is what it's for) to let it happen it will. BUT Its really easy to prevent that, interacting with character's brings up the relantionship and the shop item's also boon it by 5 per day.
SO you have to try REALLY HARD to let that focus of the game happen. Corruption/Love paths are what they sound like, Corrupting them, makes them more slutty/you have your way with them, later in the hint it's hinted you can 'share' them for money, items, story advancement etc. Not confirmed but hinted in the in-game dialog. Example. You can turn Cassandra into full corruption fuck her on the date, and she'll be 'forced' (LATER not now obviously) as a lover for the MC, after you get rid of her bf most likely, would need more content to confirm as most of it is just speculation but pretty obvious.
Love path is what it sounds like, treat em good, and they'll 'fall in love' with the mc and be the waifu you think she'll be, loyal, and yours to command. Far less fun sounding, but most peoples (YOU FORGET MUILTIPLE SAVES) main game will be how you want, and you can explore the content later. Like for me, Alexis is waifu, she's gonna be under the love route no doubt, and likely most of the other girls too, as i'd rather save then condemn them. Then on another save, hello hard mode, and more content of what i'd miss with the main game.
TL;DR: No corruption doesnt lead to NTR, that's from laziness/choosing hardmode~