I think unless there is a miracle plot pops inside the mangaka head, this series is now heading towards its death. There is no special development for ANY characters from this high school here. First it was the ultimatum from Sora's mom to Sora and Ayaka, which turned out that the mom was a whole lot more mature and loving than the both of them. No development there as Mom's head to Hokkaido. There is a huge opportunity to work on their front especially if the two of them were allowed to move to Hokkaido to test out whether the school is good or not, PLUS there is a small chance that the marriage failed so Sora's mom (and Sora, and possibly Ayaka) not going to be homeless. You can blame Sora's mom for a lot of stuff, but one thing you cannot blame is she tried the hardest to climb the social ladder for the sake of Sora. Then not even chapter 18 works by introducing someone not from the high school. It almost feels the author has already finished the very last chapter, and then just draw a bit of stuff here, and there, so that when the Guillotine chops down, it will end "nicely" and no feelings of "rush"..
The author did not use "Sara" to do a development or as a significant side story. Then she did not use her from then on, as if Sara has a sell by date.
No matter how you look at it, Sora and Ayaka's friends are not that sharp and certainly intellectual not that deep. All of them are from the same grade, but Sora and Ayaka seemed to be at least 2 grades senior than the rest of them based on their behavior vs. their friends. These friends look more like the hanging around type than the really serious type. If it were the latter, you can bet that the author will develop some plot for the group to steal Sara from her bf. But she is too weak mentally, so it was not going to work if she failed to take charge no matter how hard her friends trying to help.
To be honest I cannot imagine any exciting plot coming up; rather I am waiting to see when the chop coming down.