There is no NTR or sharing content in the game. The closest thing to sharing is a threesome with your friend and one of the carnations, but you have no prior relationship with her, and this can be completely avoided. Additionally, during one exhibition event, you can refuse to perform, in which case your friend will do it with one of the carnations instead of you. Again, this is entirely optional.
If you're a fan of vanilla games, this one might challenge you. Some moments will feel awkward, while others might make you regret not trying this game sooner.
Personally, I prefer vanilla games and initially ignored this one, assuming it was all about humiliation. How wrong I was

In my opinion, the dating aspects here are even better than in many popular vanilla games. So don’t let trolls, who often confuse their own fantasies with reality, talk you out of experiencing something truly special.