I love the way this series reads. Both Tsukiko and Aya always have each other in their thoughts and have a desire to get closer, but both seem to believe their current distance is further than it actually is, which causes them to act so reserved around each other. Tsukiko wants Aya to look her way sometimes, believing that Aya only ever has eyes for the pool. Meanwhile, Aya deeply wishes to understand Tsukiko and her feelings better, but believes that the latter has no interest in allowing her to get close.
The two of them are so close, yet so far apart. There are so many things that could be solved just by talking to each other, but like Aya said, it feels like the words are stuck in their throats. Hopefully this slow burn will pay off in the end and they'll be able to communicate their desires with each other properly.