Is this NTR?
Like, kinda. But then again the manga so far has been mostly about women forcefully throwing themselves at someone. I'd be a hypocrite if suddenly it's a turnoff now lol.
But yeah, uhh. That was a weird "arc". I feel like the point of all this should have been to show that Ao and Kurena are serious, and maybe even have another pillar of support since we just lost out on the dad's pillar. But it just made the only other onee-san in the story look like an out of touch, conceited bitch who can't take no for an answer. It's weird because this coulda all been fixed if she just crashed into them at a cafe and did most of this instead of skipping work to assault a 19-YO kid who just had to take a stand against his asshole of a dad.
She is right to be worried about her BFF(?)'s first serious relationship and that it's with a student who can barely provide for himself. She's right to call out the lack of planning and finances. It coulda even been fun to mess with them a bit if she backed of after a page or two. But instead we had half this volume dedicated to aimless drama with no real payoff except "MC knows how to say no now!". (we kinda proved that already with the whole dad situation lmao).