Cas had seen many humans in his life, and all of them were flawed, rotten or evil. Big parts of their souls were tainted of corrupt. Which is why he didn't appreciate them all that much and didn't understand the problem of collateral damage.
Until, of course, he met the Righteous man. So Righteous that the capital letter was warranted. Building up his body had taught him certain things about the man, but not everything. His personality and behaviour had come as quite a surprise to him. A confusing surprise, because he could feel the purity of the man's soul and yet he seemed to behave like a common sinner most of the time. It had taken Cas a while to understand that he didn't sin: his gluttony was his natural metabolism, his lust was a frustration that couldn't be left alone and allowed to damage his work, his anger was either justified, or explained by the fact that he couldn't deal with emotional issues at that moment: he already had too much of them. Nothing about Dean Winchester was evil. The reasons for his actions were purer than a newborn's greedy soul.
Cas figured this out after a lot of awkward staring. Which never stopped, because now that he knew, he couldn't help but stare closely at the man with admiration. And slowly, the feeling of admiration grew stronger. So strong, in fact, that it became almost unbearable. Simply standing in the same room as Dean made him gasping for breath. Figuratively.
In the end, Cas understood that the feeling was mostly love.
And the urge to tell this to Dean was pressing. He couldn't contain it. He needed Dean to know this. Needed to explain to him why he thought the hunter was the most awe inspiring person, the only person who was truly good.
So he waited for a moment in which Dean was most likely to listen to him. When Sam wasn't around. He gave Dean a beer, sat him down, ignored the frowning expression on his face and told him everything. It was difficult to express himself, more so with the hunter's surprised and outraged interruptions. But he said everything he wanted to say, in the end. And that's all he had really hoped for. Dean's anxiety at his reaction, and his slightly homophobic tendencies didn't affect him.
After all, love and anger were the only emotions strong enough for him to feel. And it was mostly love.
It had been a few months now that Cas had talked to Dean. Nothing had changed except for Dean's suspicious looks when Cas forgot about personal space. Until one night, when Sam was away again, and Dean was sitting at the motel room's kitchen table, nursing another beer. He was as drunk as the last dodo, who knew it was going to be extinct soon and was currently making the most of it.
He could feel the arousal leaking off Dean. But the hunter wasn't going out to find a girl tonight. He hadn't done so in a while. And the perception of this, converted into his body through his grace was starting to affect his vessel. And, this not being a common thing for the angel, he didn't really think of hiding his erection. And Dean noticed.
"Holy shit, Cas. Did you get a boner from staring at me?!"
"No. Well, partly. But no."
"Do you always... get that? Is that why you always stare at me?"
"No, Dean. I don't get 'boners' from staring at you."
"Then … why?"
"It's your arousal. It's almost tangible and it fills my senses. And my Grace and vessel understand differently. I myself am not a sexual being, but this vessel is, and I can't control it's reaction well."
"Oh."
Cas stretches his fingers and looks at his hands. He could feel the arousal in Jimmy as well, and it was making him warm everywhere. He took off his trench coat.
"What are you doing?"
"I'm taking this coat off. I feel too hot now."
He also took off the black vest of the suit he was wearing, leaving him in his white shirt and loosened tie. The angel sat down at the table, facing Dean.
"Cas."
"Yes, Dean?"
"Why couldn't you have picked a female vessel?"
"Is that what keeps you from intimacy with me?"
"Yes, Cas. Yes it does. It shouldn't be a surprise, bible boy."
"I assure you, God doesn't condemn homosexuals to hell as you seem to believe."
"That's not the point, okay. I've never been attracted to a man. Appreciative, sure, envious, maybe. But I've never wanted to fuck one, you understand?"
"I'm not looking for a sexual relationship."
"Look, Cas. We can't be together. It wouldn't work out."
"Why not?"
"Because human relationships don't work without sex."
"You have a relationship with Sam and Bobby that isn't sexual."
"Yes." Dean paused to shudder at that image. "But that's different. It's family. And what you've said to me, Cas, don't tell me that those are family feelings."
"No," Cas sighed. "they aren't."
"And if we were together, I would still have needs. Needs that you can't fulfil. And cheating on you, that would be wrong and you wouldn't be able to stand it."
"Maybe."
"So we can't get involved, Cas."
Sure of his argument, Dean stopped there. Problem solved, emotional issues dealt with and off the table. But Cas didn't agree.
"But, Dean, I am an angel. I should be able to figure out how to fulfil your needs. I should be able to feel how I have to do it."
"Cas..."
"I can't give up like this. What I feel... it's too strong. And it's affecting me around you."
"You can't, Cas, dammit! I'm not attracted to you, alright!"
In a quick movement, the angel slipped out of his chair, moved over to where Dean was sitting, and placed his hand on the bare skin of the hunter, over his raised mark.
"Aaah, Cas! What the fuck..."
"Please, Dean, just let me try once." Cas asked with a pleading expression. "I don't need pleasure myself, I just have to see if I can bring it out in you."
But Cas' hand on his shoulder was already tickling him the right way. It also needs to be re-clarified that Dean is very drunk, although not enough to be unable to hold a conversation, because it explains why Dean finally said yes, and let Cas try it.
The angel knelt in front of him and pushed up his t-shirt. He ran his warm fingers against the smooth skin of his abdomen, forcing the power of his grace out through his fingertips and letting his own emotions go into Dean's body.
"Oh God... What are you doing?"
"I'm letting you feel my grace. You should be able to stand it."
The reason for that, being made to be a vessel for an archangel, was left unsaid.
"Fuck, it's so warm. Ha... it's going straight to my... oh God." Dean moaned, gripping Cas' hands.
"I thought this was what you wanted?"
"We shouldn't do this."
Cas slid his hands lower, to rest over Dean's crotch and amplified the output of his Grace. The man moaned loudly. The angel squeezed his member through the jeans, rubbing against it with his hands at a fastening rhythm. Dean slipped lower in the chair, getting closer to the touch and letting the angel's hands go, his own falling next to him in a daze. Spikes of pleasure grew and ripped through the man and he came quickly, overstimulated by the Grace.
"Cas... That was... crazy."
"Is that good or bad?"
"It's good, it's fine... Man, it's fucking amazing."
The angel got up and dusted his knees off with a happy smile. He stared at Dean with heavy, lusty eyes.
"Come here, Cas." said Dean, pulling the angel to sit on his lap.
The man kissed the angel hesitantly. The stubble and chapped lips were different from familiarly soft girls. Less pleasant. And so was the lack of breasts. But Cas wrapped his arms around him and Dean couldn't help holding him tightly and feeling safe. And the angel didn't ask for him to reciprocate, keeping his word.
"I love you, Dean."
"I... love you... too."
And he did love the angel. But how could this possibly work?