Glasses dude went in line three times to buy a copy, probably hoping for a nip slip every time she bowed as thanks for him buying. I'm surprised nobody took pictures of her, I guess it's not allowed unless they declare a cosplay photoshoot session?
The way the last two pages were drawn kinda confuses me because of some ambiguity. So they got investigated by staff, but it's not made clear if they actually got into trouble (could be the plot of next chapter?) although I hate how I can't tell who was speaking those lines on the first panel of the last page. Was it Sumire, Yuusei or the new girl (probably not her)?
Anyway, this is an instance of a rookie mistake, I'm sure she won't forget critical parts of the costume next time (and wear pasties underneath). I'm impressed Yuusei actually gave her straight feedback without getting flustered or anything.