Levi has a moment where his glare falters, watching the others being led away. They'll be okay, more or less. He's certain of that, at least in a better situation than he finds himself in. The glare quickly returns to Erwin. He's wary of him. He'd be a fool to trust anything he says but Levi knows he's in an impossible position and if nothing else he is a survivor.

Even knowing that there's no other choice, it's hard to make this decision. He's hard to willingly bare his neck and give away the only thing he actually had. As much as he'd like to get out of the Underground this would never have been a path he'd have chosen.

Levi does what's necessary, though, tilting his head and exposing his throat to Erwin. His heart's racing in his chest but he refuses to give away anything. He's certain that with this bite there would surely be more than that when they were somewhere more private. He hasn't decided yet if that's something he'll fight. Maybe, he'll play along for a little while, gain this alpha's trust and then betray him when he expects it least.