Kohaku being stolen away is NTR. Kohaku going out and getting laid entirely of her own accord is not
MSG(edit: NTR* was watching Uncle Roger video in background

), it's just vanilla female infidelity. For example the groper in the main square specifically targets Kohaku because she's wearing a ring, that's NTR. He's knowingly stealing a taken woman. Kohaku going to the brothel and working, doing any of the scenes not involving Yarizo isn't NTR, it's just cheating because she's the one putting herself out there and nobody is stealing or seducing her away from Jimmy.