As he was shaking my shoulders, it seems that Erwin was behind me.
Furthermore, he somehow makes sure to avoid matching Burkhart-san’s line of sight.
I don’t think it is necessary to mention the reason for that.
“The 『Pink Hippo-san』 uses something like an illusionary magic inducing the lustful desires of people like this! Do you now understand the reason why we didn’t bring along female company?” (Armstrong)