Bare Your Neck (While You're Buried Inside Me)

Written for this spn kink meme prompt: Castiel is an alpha but, much to the shock of those around him, he's also a sub, and becomes mated to a very dominant omega— Dean. People look down on him for it, but Castiel is proud to wear his omega's collar and loves nothing more than rolling over and bearing his neck for Dean like a good bitch.