Alright, got some ideas now:

Some kinda intense rivalry between Junko and Suzuka. It’s probably the case that even back when they were in elementary or middle school, Junko’s physique was standout, so she would’ve considered Suzuka a “true” friend for rising up to the challenge in every gym class/sports day event regardless of the disparity.

And yeah, it’d be funny if there was a persistent inferiority complex or something nursed by Eikichi, who remolded himself in order to become the popular lad in school, only for a wrecking ball of a girl to decisively become school queen by doing nothing but being herself.

I think it’d be interesting for Mikako and Junko to not necessarily actually get on with each other all that well. Despite both being motherly in one way or the other, it’s probably the case more that others think they’re closer friends than they actually are. Junko is fairly tiger-mom-esque while Mikako I get is more of a helicopter mom type. Probably due to that as well, Junko, who has no social delicacy, is only uncertain around Mikako, because Mikako seems to say that she’s fine and that this “always be helpful and receptive to others needs” thing is what she likes to do…but on the other hand, how true is that?

As for Haru, I’d say that Junko wouldn’t have any reservations about being a model. He’s probably the most straightforward type, and she’d like to see him take his photography to greater levels.