I think this is the dirtiest thing I've ever written in my life. Please don't kill me if it's badly written or if there are mistakes.
Castiel essentially hates being human, he hates struggling for every single thing that the rest of the world finds normal. Yet there are those little moments, those small and big feelings that make him want to never return to being an angel, because he's pretty sure he would never be able to experience certain emotions at all. It's about those emotions he feels when Dean is close, those feelings that are hard to understand but that actually he doesn't want to understand at all.
Like the warmth that spreads in his body when Dean is there, next to him, during one of his emotional breakdowns and gently rubs his back, which is something very effective and relaxing and he still doesn't know why. Or the gratitude he feels when Dean helps him with the little human things without mocking him or making him feel ashamed. Those little chills that make his arms tremble when Dean teaches him how to cook and lays his hands on his to guide his movements. That strange sensation on his groin that turns him red in his face when Dean lets him shoot and adjusts his posture, and he can feel his hands touching him everywhere. But the moment he loves the most is when Dean rests his lips on his own and his fingers begin to touch, pull, push and stroke, just like he's doing right now.
It starts very slowly and proceeds just as slow: their clothes slip from their arms and legs and end up on the ground and Castiel loves the feeling of fabric running on his skin (it's actually the only thing he likes about having clothes on, otherwise he would spend the days naked around the bunker not to feel oppressed by all those clothes; it's not a coincidence he got accustomed to sleep naked when the temperature allowed it).
Dean kisses him everywhere, on the lips, on the neck, on the face, on the shoulders, and Castiel does the same, kissing every freckle he sees and he loves the softness of Dean's skin on his lips, loves its texture under his teeth when he bites down gently and Dean sighs, pulls him closer and makes him sit on his lap. Their members touches and they love the rush of pleasure that runs up their spines and they both moan in unison. Castiel runs his fingers through Dean's hair and sighs when he pushes forward and slides his shaft against his lover's, and he loves the sensation of having his fingers brush on Dean's light brown hair and Dean loves when Castiel gently pulls a few locks behind his scalp and forces his head back so that their eyes meet.
Castiel slowly and carefully prepares himself before grabbing Dean's member and lets it slide inside himself, and he loves the mind-blowing mix of pain and pleasure from being filled and stretched in such a sinful and lustful way, and Dean loves Castiel's warmth enveloping him in that sensual vise that makes him go crazy. Dean mutters Castiel's name and holds him desperately, hiding his face in the crook of his shoulder and wraps his arms around his chest and waist, trying to push him further down, deeper, and Castiel decides that no, this is the moment he loves the most, because his name on Dean's lips is so perfect it seems divine, and a spasm shakes him from head to toes when the sound reaches his ears.
Dean finally pushes up, joins his movements with Castiel's and they both moan, move in sync, and they love the harmony that grows when they reach this point. Their hands are on the other, Dean's hands on Castiel's back and Castiel's hands on Dean's hair and they kiss desperately like the world is going to end, creating a swirl of lips, tongues and teeth that soon makes their heads spin for lack of air. And soon, Castiel's hands move to Dean's thighs to have more support and gain speed, and this is Dean's favourite moment, because Castiel has no shame at this point, all flushed and sweaty, rides Dean without restraint, hisses his name and offers him the perfect vision of his own erect and wet member bouncing against his groin with every thrust and it's just an invitation that Dean cannot refuse.
Castiel almost shouts when Dean wraps his fingers around his length because he loves that immense pleasure he experiences when he's nearing his climax, he loves that tension that stiffens all his muscles and makes him tighten around Dean inside him, which drives said male completely mad. Dean moans Castiel's name again, and again, and he's chanting it, he bites on his shoulder and he loves when Castiel squeezes around him and cries out, his hand gains speed while the other one sinks into Castiel's hip and drives him faster and harder on himself.
Castiel chokes back a scream and turns it into a long shuddering moan when he comes on Dean's stomach, and he loves the spasms his orgasm causes and the warmth of Dean's own orgasm fill him completely when he comes as well and screams his name louder. They both sigh and collapse on the back of the couch they were sitting on, panting and shaking, and they love that little moment where the rest of the world is lost and all they want and need is the smell, touch and warmth of the other.
These are the moments in which Castiel wishes more than anything to remain human, because if that means having Dean and feeling all these intense emotion with him, so be it.
Hey, psst. This smut is actually inspired by a nsfw porn gifset I saw on Tumblr once. Well, you know, if you want to see it, just send me a PM and I'll send you the link. I'm sorry for this "PM thing", I just don't want to leave it here because I don't want troubles with guidelines and stuff.