Hm. Again, I find myself disagreeing with the scanlation in a small, but IMHO important detail.
When Oga confronted Saotome, he didn't say the neutral "Who are you?", he said "Temee ittai nanimono da?" which I would translate as "You Bastard, what the hell are you?"
These are fighting words. It's exceptionally insulting to address a teacher as "Temee" to begin with, but the real kicker is the "nanimono" question (What thing?). It implies that Oga doesn't consider him normal. And this is important because Aoi was eavesdropping. I'm curious if she's finally going to be filled in on what's happening
Other than that, Hilda shows her ugly temper again, and Saotome is established as "not hostile" towards them. Zerub spell or not, I have difficulties seeing him as a mere ally. There's more to him than meets the eye so far.