Scarsor here.
I really didn't think I'd have to explain it, since the situation is pretty clear when you play this game, but since people are interested in it and they care about it, I'll try to explain everything. Spoilers.
No one is going to sleep with strangers behind the protagonist's back. The girls can sleep with each other, even if it's just the two of them. Yes, that can be skipped, just like any other content that might evoke mixed feelings. And as I've seen, anything can evoke mixed feelings, but whatever.
Phew, that's a pretty long explanation, isn't it? I did spend less time and effort on my graduate dissertation, heh. Probably the only way I could present the issue in its full complexity. I hope it's clear afterwards what exactly I'm up to and what happens next. Thank you for your attention.