A/N: Before you begin reading this I highly suggest you listen to watch?v=opEZ9OAbkJ8 while you read. It helps give it a bit more of an emotional feel. This was also inspired by a dream I had a while back, which was about the end of Supernatural. I hope you enjoy the feels this oneshot!
A man in a trench coat was standing in a graveyard by himself, looking down at one of the graves sadly. Castiel took a deep breath and shut his eyes for a moment before he finally spoke.
"Hello Dean. It's been a while. It's only me this time, Sam is on a hunt at the moment." He opened his blue eyes and let out a long sigh. "It's been quiet without you at the bunker. Sam also misses you greatly."
He then drew a sharp breath and added, "I miss you as well. It hasn't been the same without you."
His eyes lowered to the ground as he tried to find his voice to continue on. He looked at Dean's name on the marble stone and he opened his mouth once more. "You were always there for me, and no matter how many mistakes I made, your faith in me never ceased. But this time... this time my failure has had a greater cost. It cost you your life. I know that even now, you would tell me it wasn't my fault... but it was. Because I was supposed to be there to protect you, like I promised myself I would. But I failed. You were the most important person to me."
He cut himself off, trying to swallow the lump in his throat and his voice quivered as he tried to finish. "I always valued your kindness, and you were the bravest man I've ever met. And I never told you..." He put a hand to his face and could feel hot tears streaming down his cheeks. "I love you, Dean. I always have. And I am so sorry."
His voice cracked as he said this and he slumped to the ground. He could feel drops of rain falling on top of him, but he didn't care. It was then that he heard a voice behind him and he turned around to see the youngest Winchester looking down at him.
"S-Sam..." He choked out, trying to compose himself. Sam kneeled beside him and pulled him into a hug, slowly rubbing the angel's back as Castiel cried even more. After several minutes of sitting there, comforting the angel, the brunette man finally pulled away.
"We should get back. I need your help with something."
Castiel nodded, wiping his eyes on his sleeve and slowly stood up. He then paused for a moment, looking up at his friend as he spoke. "You go on ahead. I'll meet you there."
Sam opened his mouth to object, but once he saw the pleading look on the angel's face, he nodded. "Alright. Be careful, Cas."
Once the hunter was out of sight, the angel turned to Dean's grave one more time before slipping off his trench coat and draping it over the tombstone. He ran his hand over the name carved in the marble with a sad smile before he turned away and walked off.