Good Omens: The Pharaoh's Son (Aziraphale x Crowley)

Crowley and Aziraphale have known each other for a little while, just a few millennia. But, something is coming, something that has Aziraphale very, very worried. Crowley can't just up and leave no matter if the angel begs and pleads, probably. This is the demon and the angel's first big falling out that will change...