Lol'd at the "Didn't you use to mind your own business" comment.
Also, page 10 confuses me. I thought the little sister already had a guy she was talking to that was kinda younger. I might be mistaking her for the Childhood-Friend girl though. They have similar hairstyles.
The joke on page 10 is that it's "Respect for the Aged day" holiday, and that's why the little sister has been helpful all day long, and why Ai-chan and mom are pissed when they realize the reason why.
Getting shut down with the "I already have plans" when he'd already worked up the nuts to ask her out and see if she was actually interested in him hurt me.