Jill even said to herself once the mc'd left, "(You could have made out with him all night and let him stay over. How about that!?)" So it's not like a foreign idea. The mc has been so forward in all his sexcapades, for him to leave with his tail between his legs seemed out of characters.
Dont think so that the MC is out of charactre in this scene...
You have to be very attentive to get it, but several times the MC has thoughts to change his behavior overall, especially to girls and after Hell Week.
Especially if you play as "chick" it makes perfect sense that he is not going to push Jill here to anything, not even to stay a little longer... and especially for Jill the MC has a very good read if she is uncomfortable or not (the first time he runs into the auditorium while Jill plays for example)
Jill makes it clear that she has mixed feelings about the fact that the MCs ignores her wish to not see each other too openly and just showed up.
All this in mind its understandable that the MCs leaves.
And for being forward with other girls... The MC is kinda "manipulative", his behavior depends on the girl. He adapts his behavior. In my opinion the MC has a gift to adapt his behavior to a perfect match for the girl in front of him if he wants to. And in certain scenes (and monologues) its getting obvious that he is aware oft that, but also aware that some actions will have consequences.
Before College the MC has no clue about love, relationships or girls.
Now he comes to college and is blown away from all the girls and rushes in one crush after another (and is aware of that a little later on)
With Jill its very different. Jill is the first Girl for the MC were love is growing. He said to her in EP6 that he is falling for her... thats a first in the entire game so far. All the other girls are just "crushes" to this point, nothing more. (sex has nothing to do with feelings in this game)
So at this point in chapter 7 he has very deep feelings for Jill, and the relationship to her ist very vulnerable. And he knows that... to go to Jill here was a big risk, and to stay and even bigger risk... Jill makes this clear too.
And in every scene with Jill its getting more and more obvious that she is very anxious when it comes to sexual contact. And the MC learned this (couch at Bella's)... so leaving here is the right thing... Jill was sending clear signs that its better he is leaving, despite her feelings. And over the time the MC understands how he has to handle Jill. doesnt matter how forward he is with other girls, other girls are not Jill, and he knows that.
