Huh. I dunno if I've ever felt this before, but maybe this should've just been a one shot. This is...frustrating to say the least. I think I'm gonna reread the other chapters to see if this feels anything other than out of left field, because it just...didn't sit well with me at all. I get a story needs something to be in conflict or flux, but that could've easily been stuff outside their relationship, rather than just shoving in a random love triangle out of nowhere.
So I did go back and re-read it, and this didn't just come out of nowhere, they clearly set up that the senpai was obsessed with Akane, she got super flustered multiple times being around her. But this still feels really aggressive on her part.
I think the reason this feels odd is that Kyouko and Ritsu's relationship is brand new, and Kyouko feels justified now in her fear, even though Ritsu should be able to go out and see friends. It's rewarding Kyouko's paranoia, which feels bad in the long run.
I'm definitely not at a point I would stop reading it, but I do want to see the two of them make this right soon. For a story that started out with a formerly unrequited love becoming mutual, I wanted to see these two explore their relationship more, not fight over a love triangle. Could've given it a few chapters to breathe.