Hey, most of the girls do not have an NTR or Sharing path. Of the nine girls, currently only Scarlett, Mary, and Bella have paths involving other men. Mary also has a clear non-sharing path. Scarlett and Bella do have a non-sharing option, but they are having sexual relationships with other guys, but that would be all be pretty much done off screen so you wouldn't see it. Gabriella is also sharing, but hers is MFF. It is possible I may introduce something in the future with the other girls, but it would all be optional and avoidable.
And precisely because the sex with other guys keep happening offscreen, I haven't even started the quests "Handyman" and "Three's Company" and I won't start them. I shouldn't have started the "teen crush" quest either, but at least you can tell Gabriella that you're not interested in her.
So I hope that if other LIs have the participation of other guys in their paths, it's something completely avoidable (that is, it doesn't happen either on screen or off screen)
Yep, the ones that currently don't have participation with other guys may have an optional path introduced later, but this will definitely be completely avoidable and won't be happening off screen either if you choose not to go for it.
Any future paths would be similar to Mary's one, where it's a clear inclusion/exclusion of other guys participating.