For most of the game, Evelyn (potential love interest) spends time negotiating with Thaddeus (representative of the royal court, plot advancer and skill point dispenser). It turns out she uses *all* of her assets when negotiating. If you try to "talk to Thaddeus" when Evelyn's portrait is next to his on the game map, you get to see those negotiation skills in action. If you never try to talk to him when he's "meeting" with her, nothing happens.
If you try to speak with Thaddeus at the wrong time, you get the choice to interrupt them (ends all NTR content, makes Evelyn much easier to romance, also ends a small weekly payment from Evelyn), or watch quietly (no effect other than getting to see the scene). If you watch, then the next time you try to talk to him when he's with her, you see a different scene (there are three scenes, in order: kissing, oral, and anal. You must see all three to unlock the entry in Evelyn's gallery). You can always interrupt regardless of how many times you've watched quietly.
What I usually do is never look on or interrupt them until I am ready to begin romancing Evelyn, then barge in on them and make them stop. But it's also perfectly possible to interrupt them sooner - anytime after day 7 in game. You lose out on a tiny bit of extra income, but this is not a game where money matters much at all. You can also never watch or interrupt them at all, but that makes Evelyn *much* harder to seduce.
There is absolutely no other NTR content in the game.
