I don't know, I feel if this entire manga should be about how the 3 bullies start to develope romantic feelings towards Ueno it would be so much better.
Manaka is really a pointless character, a very weak filler character, but on the other hand takes so much space away from actual happenings.
Also it's very clear Chisaki is the main girl and her and Ueno has a thing for each other, yet their relationship and character pairings got zero built up, they had nonexistent chemistry and we are basically at the end of the manga. Instead Tsubimo got built up pretty well with Ueno, but she is clearly a side character but even she got vaporated because the thing Manaka exist...
I feel this manga gonna end very soon and there is no good end here. Whatever happens, Chisaki x Ueno never gonna feel good, because the author doesn't built them up, Tsubomi x Ueno is cute and all, but it always going to feel lacking becase she never treated more than a side character, if Manaka x Ueno stays, that is a straigh up cucking the reader moment...
So I'm sure it will be dissapointing, no matter what the ending will be.