Lan Wangji endures the inspection and small tugs gracefully, though without slowing down his steady walking pace. There's a moment where he almost expects her to try and stick her head into the opening of the sleeve, but she seems to realize she's too old for that, at least. Her peeking around the sleeve like a curtain rather belies that thought, though.

When her investigation is concluded, he swiftly tucks his arm back between his guqin and the small of his back. With the arcing movement, the folds of his robes fall into place again like particularly elegant plumage.

"It is customary." Customary for what, he doesn't elaborate. Apparently she isn't aware this is not a color one commonly wears to festivities.