I don't think I'll ever understand why people get so hung up over who or what girls get fucked by in games. Beyond the visual aspect I mean. That I can understand.
Either way, unless there's some plot that allows the protagonist to lose one or more girls after he got into a relationship with them, this game doesn't have NTR. It's always a choice to prostitute any of the girls. Don't want them fucking with anyone else, don't prostitute them. Easy. You'll miss scenes, but that's like saying that you'll miss scenes by not playing a game with a fetish you don't like, it makes no sense whatsoever.
The only complaints that seem objective are the one made by that one guy that was commenting about the research tree and the complaints about the combat mechanics being weird. But all this bitching about the brother aspect of the game when it's part of the description explaining that the princess wants to make money by whoring herself out and any other girl she can convince is really really weird. It's not like it was hidden...
They even mention the MC from the start. Like. Isn't it obvious that the MC isn't going to be exclusive with the girls if there's tons of prostitution involve starting from the very top with the princess?
Ugh. I swear. This shit always comes up with male focus characters. It never comes up with fem-protagonists, because then all the peeps that want to self-insert don't give a crap...