There are sounds escaping in Crowley's breath again, each time just a little bit louder, each time just a little bit more urgent.

It shouldn't be - possible. It shouldn't be possible to keep going, for Aziraphael to push him higher and higher and, every time Crowley thinks he's reached the limit because surely, surely there can be no more, to ratchet it up again (and again, and again) until the pleasure thrumming through him is nearly excruciating, because it shouldn't be possible to ssstill leave him aching for -

Crowley writhes under Aziraphael's mouth, shudders with each sharp nip; his back

his back  twists   and  strains   and finally (finally) arches in unashamed need.