I thought it was rather new for Yodokawa to create a story where the older girl takes initiative chasing the younger one for once, but nope, it was the younger chasing after the older, again :))
This is just like that one P.G. Wodehouse novel where the guy fixates on a cute girl in a photo in a magazine and then meets her in real life and freaks out.
I like how it turned from "she is not my type" to "why do I blush when she smiles?". It is like that in real life. Some person might not be your type but spend a lot of time with them and they suddenly turn a lot more attractive.