[quote=@Kazemitsu]
The way I read it made me think your guy thought he was quaking with anger or fear XD
[/quote]

That would make sense where he was sitting. "I don't fucking know these people, but they sure seem to argue, and he looks ready to slug someone."

But his perception was also because of his dense mass... he gives a big OOMPH where ever he walks. So it is also him being slightly surprised. 

And Then Cas just ginerly nods to him. "We is family now." 

I love how I can just be horribly reductive of my own post. XD