This might be a false alarm, but I can't help but feel concerned for Utsugi. The bubbly gyaru thing is a mask. Gonna bet all of the money in my pocket that she caught this Aoi and Mao making fun of her behind her back, and realized she doesn't have a single genuine friend in her life, and it's almost broken her spirit. Her last hope is the one girl in the class that is completely incapable of and unwilling to fake civility. I've been thinking this ever since Utsugi fell asleep on her shoulder on the train, saying that for some reason being around Hiiragi makes her feel sleepy. She is so dead exhausted from having to keep up the act...
It's a testament to the quality of this manga so far that I'm even contemplating all of this, even if it turns out to be complete nonsense and she is just a bubbly gyaru caricature. The characters don't feel like straightforward archetypes; they're always capable of surprising you with hidden depths. The main characters are such precious weirdoes, but there are these moments, when they show just how close they are and how they're wired to support one another, that I can't help but adore.