Well...he guesses that is true, they do know. And it looks like whoever this fellow is, he isn't particularly concerned about what others are doing as long as it isn't affecting his work, there. Which is peculiar on it's own, to say the least...

His curiosity is piqued too much for him to not ask, even if he has a feeling that it would be better if he left him alone, probably.

"What is all of that?" Izuku questions carefully, folding his hands in his lap now that he's glass-free.