when, by who, and do you mean "female form" as in the sissy form that still has a dick and a flat chest? because yes a sissy is an effeminate form but i wouldn't go as far as calling it a female formyou sure we are playing the same game? she can get fucked in her female form. I understand the ntr bit not making sense cuz they loosely like him because he's there. I'm guessing as long as you don't proceed the girls through all "ntr" scenes, they won't be taken by someone else. I'm not sure if your scenes with them is tied to their scenes with the other men or not though
the only scenes i saw at every point were the ones with the girls, doing something for them, then they get fucked by someone, MC never gets fucked and never becomes a female