Yeah, I simplified things for the sake of not overextending the comment, but I'd argue every girl but Josy has something that made them grow closer and closer to MC.
Josy: She's already your crush as you start the game. All of a sudden she decides do be very flirty with MC for some reason. She hooks up with you a couple of times, kinda disappears, comes back as Maya's GF, and now you're already discussing relationship status.
Jill: She's meant to be the angel character, so she meets MC as she's trying to help him. But that's just who she is, she'd do that for anyone. However what sets MC apart for her is that you're different than all the snobs she's surrounded by. You're a simple guy, yet you're indifferent to her money and status, and you're not out to impress her like the other guys do.
Sage: Notice I said "romance" and not "sex". Sage has a much more casual vision of sex, so it doesn't mean much here. That aside, you can see them growing closer on other aspects. She starts off blackmailing MC into helping her, but from that you grow into being her confidant, and eventually her friend. As her relationship crumbles, you're the guy that's there for her, listening to her frustrations, and providing her sexual relief. I'd argue she's still in the "growing closer" phase, rather than "romance phase". She's still getting development, as she never thought of the MC as something more than a casual fling, but we're getting there.
Bella: Has a shitty opinion of you, but gives you a chance because of Jill. She's very reluctant to you at first, but comes to know you mean no harm (in chick route). Again, wouldn't say they are at a romance level yet, but definetly growing closer. She's drawn to MC because she's a fairly lonely woman, deemed an "ice queen", but she sees you trying to crack through the ice. Plus, she has unresolved issues with her housband, and you can tell that deep down she craves for affection.
Sorry for the wall of text. If you got this far, here's a photo of a kitten as a reward:
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