I love how this manga has fully made people take sides in a situation like everyone here doesn't suck to some degree.
Yuni's only a cunt because Nanase's historically an insensitive one-track-mind moron. Yuni absolutely needs to communicate more clearly, but it's not completely off-base to assume that Nanase should maybe put in an ounce of effort every now and then, and not only when it's convenient for her.
Yuki's doing to Yuni what Yuni did to Nanase by proxy of Fuuko, only she's not even trying to hide it, and Nanase is fully enabling her without even seeing the problem. And she gets to be self-righteous pretending she's "protecting her best friend" like she's not just following her own selfish whims in a weird hero-complex delusion.
Fuuko's damaged (and apparently for reasons beyond her unrequited love with her onee-san) and selfishly pulled Yuni into a pile of dramatic fuckery for her own amusement, and Yuni went all-in and fucked up hard - and is still paying for it even as she tries to put on a brave face and make an effort for Nanase in this mini camping arc, only for Nanase to--seemingly obliviously--just throw it all in her face.
Meanwhile Yuni has apparently abandoned Fuuko to whatever past trauma has resurfaced in the form of that Glasses Brunette chick, who seems to potentially have a history with that Music Sensei as well.
It is indeed one giant trash fire, and none of them are good people, but it's great to see who people root for as though any of them are redeemable at the moment.