No one could. At this point Koto isn't in love with Aya, she's in love with the idea of girl who existed 7 years ago and won't be here that much longer. Aya will inevitably start to change and her current self won't match that ideal Aya Koto has inside her head.Let me guess, even Aya can't fill the Aya-shaped hole in Koto's heart at this point.
The point is to explain her obsession and prepare for what's to come.Well, this was useless alright. Who in their right mind would read up until this chapter and not understand that Koto really, really loves Aya from her childhood? What's the point in hammering it down so much? We could have some plot development...