Levi would have a thing or two to say about surviving a Titan chewing off his arm not being earned, but by the same token, he would understand; effort versus circumstance, maybe. It still means that he survived. And managed to be the one to actually rescue Eren and make that mission a success. It'd been no small accomplishment.

(Nevermind that it took Levi himself some time to not think about how the outcome might have been different if he'd been there if not for his own injury, but that's water far under the bridge at this point, one he's long past dwelling on. Mostly.)

He does help with the straps, more than practiced at it now. There's intimacy in this, too, and he's been quietly glad to see Erwin thriving with the arm, now long used to its touch. Even so, he settles nearer to Erwin's left side, to feel his warmth better.

"Mm," he intones mildly, curling up against his chest again, resting his chin on his hands and just gazing up at Erwin lazily. "Not bad."