there are 2 types of NTR, one is about the MC having someone they love "stolen" from them. the other is the MC doing the "stealing", im of the camp that its fair for the MC to "get them all", because someone is no longer a virgin doesnt mean they are in anyway less worthy, so if a character already has a boyfriend, and you take them from those guys, its ok, so long its the player choice. OR, the other guy is a massive douche. since, as a friend used to say, there's nothing wrong with fucking a cunt!