I think it's because each of them still don't know how the other one feels, from both of their perspectives, their feelings are best described as unrequited love, when one of them answers the other's feelings with love it'll stop being unrequited love, so far they barely interact, there's no exchange and as such none is answering to any feeling.Ooooh Masuda-sensei is really getting into these cliffhangers! Love it!
Just a quick note, there has been a question before about the use of the phrase "Unrequited Love" (片思い). I have checked and double checked and this is what's written in the raw. Now, I know that it might seem wrong but after thinking about it (and discussing it with readers in the Discord channel) it's very possible that Masuda is trying to emphasise that Nayu-chan, although she likes Hikoichi, isn't aware to what extent yet. This is the consensus we came to, but what do y'all think?