i looked and i can't seem to find those guides you madeIf you know what youre doing, you can completely shut down any semblance of NTR. Unfortunately, this is a game of numbers. NPCs act according to those numbers and never do anything more than that.
As for the story? Its a sandbox. Make your own story. Mine is usually playing monogamous, while fending off all other guys from my girl, or polygamous, and cucking everyone mercilessly. In both cases the end result is that all guys are effectively shut off from ever getting laid, since even if i do play monogamous, i will still abuse my love count to keep them away from chicks. Thats not NTR - thats just being cruel on my part.
I wrote a number of guides about this game. One is about not getting cucked. You just have to look for em in this thread.