Author's Note: Because of such positive feedback, I am proud to announce that I have decided to make this story multi-chaptered. It will follow a loose plot (still working out the details) and I don't know if updates will be all that frequent since I'm only adding to this story when inspiration strikes (but I have a lot more chapters already planned out in my head because Destiel with Demon!Dean is probably one of my new favorite things), but I will try to update as often as I can. Thanks for the reviews and I hope you are pleased with my decision to continue this story.
Castiel liked to say he hated him. After all, there were a lot of things to hate regarding this twisted version of the Righteous Man—so emotionless and taunting and rude and cruel that Cas always found himself wondering which was the best way to deal with the problem: smite this vile, malevolent monster and save the Earth from his inevitable reign of darkness and torture, or allow him to walk free and continue to manipulate him and his loved ones just for the sake of his sick entertainment.
And like the selfish coward he was, Cas always went for the latter.
He wanted to hate him—for what he'd become, for all the horrors he had committed and would eventually commit in the future—but Castiel knew deep down, he could never feel any inclination of hatred towards the man (demon, Cas corrected himself sharply, he's not a man anymore). He was too beautiful, too kind-looking, too Dean. Castiel could never hate him. It didn't matter if he wasn't really "Dean" anymore. He was wearing his face, and that was all it took to render the Angel of The Lord putty in his hands.
Dean would laugh at him sometimes for being so wistful and staring at him with a nostalgic and heartbroken glint in his blue eyes. He would pin the angel down to the bed and kiss him deeply and dirtily, whispering hoarsely against his spit-slick lips, "That Righteous Man you adore so much is gone, Cas. I'm not him. Not anymore." He'd chuckle then, like Castiel's misery and despair over the fact actually amused him, and start planting sloppy, possessive kisses across Castiel's firm planes of skin, "And good thing too because he would never grow the balls to do this," He bit a bruise into Castiel's collarbone, making the angel cry out, "He could never give you what I can and will. So you better stop looking at me and wishing it was him."
Later, after their act of sick, disgusting passion, Dean would allow Cas to lay his head on his chest. With a guilty conscious and blissed out mind, the angel would let the rhythm of the demon's deceptively steady heartbeat soothe him into a state of tranquility and slumber. But just as Castiel's mind flirted on the edge of sleep, he would stretch his awareness and find Dean staring down at him with an oddly raw expression on his face, his eyes and the sour twist in his mouth indecipherable as he absently traced symbols and sigils into Castiel's skin.
Castiel liked to believe that he was changing him. Sure, it was a lost hope concocted by his brain to justice doing this—whatever this was that Castiel was terrified to put an official name to—with a demon, but a hope nonetheless.
Author's Note: Reviews, follows, and favorites would be appreciated.