At first Levi frowns at him, nose scrunching a bit, because he definitely doesn't get the joke.

But Erwin's laughing - giggling ridiculously and giddy, and he decides that whatever the reason for it doesn't matter, because it's one of the most precious sounds he's ever hears.

At once, practically all of his anxiety lifts away, because he can't think about anything else being more important than this. Levi huffs in fond, loving exasperation, and wraps his arms around Erwin's neck to drag him closer, as though he could absorb that laughter directly into his skin, keep it in the marrow of his bones. He hides a smile against Erwin's throat as he grumbles out:

"Well, you are a fucking weirdo, that's for sure."