The only multi-girl setup that makes sense is Bella and Jill. Simply because they are already so close.
Sage is a jealous girl, she would probably stalk MC to death if he tried it. Josy and Maya? Well, maybe but I doubt it. They are both too insecure for it.
The interesting thing is so far, the game has been pretty linear (as far as any real branching goes). You can avoid sexual things with the girls, but you still interact with them all regardless. I wonder if that will change in the future. The first couple chapters are mostly introductions, so I assume it will.