Perhaps Crowley can read the message in the way Aziraphale's shoulders tense, or perhaps his own wants change. At any rate he kisses Aziraphale's back, then withdraws his fingers. "Turn over, angel," he murmurs. "Let me see you."

Let them see each other, let them both be seen. As soon as Aziraphale is able to watch Crowley grins wickedly and licks at his fingers, forked tongue on display.