i like to imagine that while in purgatory, in between fighting and running and too few hours of sleep, Dean and Cas had a lot of long hours in hiding with nothing to do but talk. at first they would talk about everything and nothing, as long as it wasn’t about them, he’d tell Cas anecdotes and sci-fi trivia, Cas would recount legends about what other mysteries lurked in the woods. when they finally did talk about everything that happened, everything they’d both lost and every way they’d hurt each other, they argued, they fought, but in the end they came back to sit beside each other under a craggy overhang of a cliff and realised they felt lighter. after that, the darkness wasn’t so deep.
when Dean gets back topside he finds himself idly throwing out comments still, sometimes they’re things Sam already knows and he looks at Dean confused and says “dude, I know, I was there," and Dean just blinks, slightly shaken, realising finally what he’s been doing. so when he finally does see Cas again, he greets him in a hug and a relieved sigh as he finds his pieces slide back into place.
"I have so many things to tell you," Dean says against the side of his cheek.
Cas pulls back slightly to look Dean in the eye, mouth quirked in a slight smile, fond in that familiar way that Dean is so happy to have back again. “They can wait,” he says, and closes the space between them with a kiss.