Crowley ignores him at first, just to have his turn at being contrary. Even when he relents, starts to move again, he doesn't continue down - not yet. Instead, he detours to the side again, teasing his breath and the very tips of his tongue along a very particular stretch of Aziraphael's side.

('Sensitive' is one word for it. 'Ticklish' is another. Turn and turn about.)