@Wildstag : I'd surmise he's her grandfather like @Bogdan6222 said. Most likely explanation in that particular holiday theme of respecting one's ancestors, methinks...
@Kneel_Breen Apparently they're broadcasting an interview of Imouto-san taken earlier that day, and the on-screen text says "Respect for the Aged day / Street-side interview / What are you doing for old people?"
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.
Just a little note on the shop's name: it's based on the Super Kamiokande which is a neutrino detection experiment (hence NDE) sited in a mine near Kamioka city.
@saito197 @FrozenEye Says on volume 3's characters' bios that no one has ever seen Miku with the headphones over her ears, so it may well be that she doesn't actually listen to music...
regarding TPO it's "time, place, occasion" and is mostly used when someone does something inappropriate.
https://www.urbandictionary.com/define.php?term=TPO
https://en.wikipedia.org/wiki/TPO
Those glasses are like $210 a pair... 😲
I cringe imagining how many the customers are breaking per night, what with having no tables to rest them on and being tipsy...