I'm sorry
The day when Dean dies is not a significant one, it's just a normal day and a normal death. There wasn't a witch or a vampire nest...it was peaceful and he slipped away whilst dreaming of simpler times when he was still young and everyone he loved was still alive.
Cas is the one that finds him, it was never really going to be anyone else seeing as Sam bit the big one a few years ago and Jack was still sleeping.
He finds the hunter he rebelled for lying on his comfortable bed in the room he loves looking Serene and worry free and for just a moment he turns to leave Dean to dream until his heart plunges and his knees threaten to buckle beneath his weight.
For a while he lets himself fall apart and feels the full magnitude of his loss and all that he'll never get to have - in all the years he's known, and loved, Dean he has never had the courage to truly tell him how much he means to him.
Now it's too late...Dean will never know.
The realisation stuns him for a while until he comes to his senses and remembers who and what he is.
He finds Jack and he tells him goodbye. He tells him he'll come back when he can.
•••
Up in heaven Dean takes his seat at the bar in the Roadhouse, laughing and smiling with Ellen while Jo gives him shit for dying in his sleep instead of going out in style. They're all happy and though there's an air of sadness that Dean finally kicked the bucket it's not like he hadn't expected his death for his entire life. Hunting is perilous and it's a miracle he made it to the age he got to.
Sam comes out from the back and the brothers cling to one another while tears fall down their cheeks freely. It's been too long.
They're young again. Happy. Together.
But still, something is missing.
He doesn't know what it is until Cas materialises in his worn trench coat with a watery smile and a laugh that sounds relieved, everyone is suddenly very preoccupied as Dean closes the distance between them.
"You took your time." He rests his hand on Cas' shoulder and huffs out a laugh.
Cas just stares for a moment before reaching up to cup Dean's cheek, "I'm sorry."
The unspoken 'for not being by your side' hangs in the air between them but Dean doesn't wait for more to be said, he pulls Cas in by the lapels of his coat and seals their lips together - pouring all his love into his angel.
Cas returns the kiss, sliding his tongue past Dean's lips and exploring the contours of his mouth with reverence - everything they've always wanted to say passes between them and it seems to last eons before Sam coughs and Jo bursts out laughing.
"'bout time." Bobby grumbles as he cracks open the bottle of beer Ellen hands him and holds it up to toast the two men.
Dean's smile is blinding and Cas feels as light as a cloud.
•••
From that moment on Cas spends the majority of his time with Dean, only going back to see Jack and help his adopted son.
When Jack decides to join everyone Cas stops going to Earth altogether - all the people that matter are in one place.
Ages pass them by, the Earth continues to go on and long after mankind has forgotten about the Winchester brothers Cas and Dean remain together. Happier than either of them ever expected to be.
Of course it's not all perfect, they argue sometimes about different things - mostly stemming from Dean's insecurities and the belief that he isn't enough to keep Cas entertained. But the arguments are short lived and never last more than a day, they always make up before going to sleep and they always share a goodnight kiss.
