"You can't stay."
The heart in Cas' chest, that beating thing he had slowly become accustomed to, seemed to stop completely at Dean's words. While he was still trying to understand socially acceptable human conventions, he hadn't thought he'd done anything in the short time he'd been in the bunker to incur Dean's sudden hostility.
He stared at him in disbelief, his stomach twisting uneasily, his hand tightening over his forgotten lunch.
Dean was the first to break his gaze away; his eyes, like the darkest shade of cut sea glass, were shimmering and pained as he looked down at his hands.
Cas shared a bond with the man standing before him, a profound one, and had, even at the worst of times, been able to read into Dean's emotions somewhat, could sense a pale echo of the feelings he hid so well from others.
But now, with his grace stripped away from him, Cas was helpless to understand Dean's motivation for suddenly pushing him away. He tried to reach out mentally, to find a reason, to find out what he had done wrong, but it was like groping for someone in the dark; he was completely shut off.
Cas swallowed hard against a dry throat. "I do not understand."
Dean drug his eyes up, centering them on Cas again, his eyebrows drawn together in an expression that seemed to be a mix between grief and regret. "It's just that," he broke off, scrubbing a hand roughly against the back of his neck. He closed his eyes for a moment, huffing out a deep sigh before continuing again. "It's the only way I can keep Sammy safe. And I can't tell you why." His voice broke over the last word.
Cas felt like he understood less now than he had only a moment ago. His heart, which had just felt numb and cold in his chest, suddenly hurt, like it was breaking into hundreds of fragmented pieces. The pain he had only just begun to experience in his human form, including the fatal wounds he had received at the hands of April, didn't come close to the pain he felt now: a sharp, hollow ache that made it hard for him to draw a breath.
He slowly nodded his understanding, though he did not understand at all, and stood up from the table on shaky legs. He knew, possibly better than anyone, Dean's fierce devotion to his brother, and rightly so; the Winchesters had been through more trials and hardships together than any family had any right to be subjected to, and they had fought through them together, had protected one another from the evils of this world and the next.
But it had never been Cas' intention to hurt Sam in any way, deliberately or not. He could not grasp why, suddenly, Dean saw him as such a threat to Sam's safety. He could only walk away, could only honor Dean's request as a repayment for all that Dean had done for him.
He turned to walk back toward the sleeping quarters, to the room he had claimed for such a short time, just to grab the few necessities he had brought with him. His toothbrush, two wrinkled dollar bills, his angel blade, still stained with his own blood.
"I'll set you up in a nice hotel, close enough to keep an eye on you." He heard Dean's voice behind him, but he did not stop or turn, only kept walking, afraid of what would happen to his already pained heart if the look on Dean's face came close to the uncertain and wounded pitch that was already in his words. He kept walking even as Dean called out his name, the sound of it a broken plea.
He made it to his room without looking back, made it over the threshold without looking back, before the tone in Dean's voice became angry and desperate. "Dammit, Cas!"
He suddenly felt Dean's hand on his shoulder, grasping him and turning him around to face him and slamming the door behind him. Dean was breathing heavily through flared nostrils, his mouth set into a grim line. His eyes were a deep hunter green in the dim light of the bedroom, glinting with something Cas could not name.
He stood stock still, blinking away the tears stinging the backs of his eyes, baffled at why Dean was stopping him from leaving, when he had made it so clear that did not want him to stay.
And then Dean's mouth was on his, smashing their lips together in a rough assault. Cas released a muffled and helpless cry as Dean fisted his hands in the fabric of his sweatshirt and pushed him back up against the nearest wall. He grunted out a breath at the impact and could barely drag in another when Dean's tongue pushed past his lips, probing insistently against his own tongue, sliding between his bottom lip and teeth. The kiss was a rough thing, full of desperation and fear and guilt, nothing like the sweet, delicate kisses Cas had received from April or even Meg.
Cas could feel his body responding to the feel of Dean's mouth on his, and was not entirely surprised to find he enjoyed the scrape of Dean's stubble against his chin. He rolled his hips forward, the erection suddenly swelling and straining against the inside of his jeans pressing against Dean's thigh. A tight coil of arousal settled heavily in his stomach at the feel of Dean's hard cock pressing back just as relentlessly. He was breathless and wanting as Dean pulled back and rested his forehead against Cas', fighting to drag in panting breaths.
"Goddammit, Cas, I've been waiting too fucking long to do that," he whispered gruffly.
Cas could only nod against Dean's forehead, his hands moving up to Dean's jeans, his fingers settling in the belt loops. It was something he had desired ever since he pulled Dean from Hell, ever since his own handprint had been burned into Dean's skin, an unspoken mark that had bound them together.
He swallowed and licked his puffy, kiss-swollen lips, ignoring, if only for a moment that aching hurt that still clenched at his heart, that small voice that spoke that unwanted truth: Dean was pushing him away. And Cas would oblige, would leave this place, would give his own life for Dean if it came to it. But if all he had was this one moment, he would take it and cherish it for as long as he was physically able, catalogue it and pull it out and examine it on the inevitably endlessly lonely nights he was to endure.
He pulled his hands from Dean's jeans, sliding them up the hard plane of his chest, tangling them in his short hair. He tugged the strands back gently, bringing Dean's head up to look him in the eye.
Tears were crowding Dean's eyes and his bottom lip trembled almost imperceptibly. "I ain't got a choice here, Cas." His voice wavered.
"I know, Dean." Cas brought his lips up, settling them against Dean's mouth, pouring as much understanding into his kiss as he could,tasting the salt of Dean's unshed tears in it, tasting his own, because while he still did not really know why he must go, he simply knew that he must and tried to wordlessly convey that to Dean as earnestly as he could with the movements of his mouth.
Dean quickly began to return the kiss with a hungry fervor, and complied with a small moan as Cas started walking him back toward his bed. Their lips broke contact long enough for their weapons and clothes to be discarded in a hapless heap on the floor, and long enough for Dean to grab the bottle of lubricant out of his jeans pocket.
Cas fell back on the bed with a soft grunt and Dean crawled over him. He brought a hand up to the anti-possession tattoo on Dean's chest, gingerly tracing over the star shape. A shiver wracked visibly through Dean's body at the touch. Cas stretched his neck up and stole another kiss just as Dean slicked his fingers with the lubricant and pressed one into him tentatively. Cas gasped and fell back onto the bed. The feeling was mildly intrusive and he instinctively clenched down on Dean's finger as it slid deeper inside.
Dean brought his head down near Cas'. "I'm right here, Cas. Just relax," he said softly, breathlessly, against his ear.
Cas nodded, feeling his body loosening against the mattress, just as Dean inserted another slicked finger, stretching him open slowly. His body accepted it, the burn that had been present only a moment earlier melting into a warm pleasure that curled from his belly outward. His cock stood at attention under Dean, jumping eagerly when Dean's stomach just barely brushed the leaking tip as he moved forward to press a soft kiss to his mouth.
Dean's fingers continued to work in and out of him, slowly building a tortuous tempo that had Cas rocking back to meet the thrusts, then he suddenly stilled, eliciting a frustrated groan from Cas.
"Dean, please," he pleaded breathlessly.
Dean's gaze locked on his, the green of his irises almost swallowed completely by the darkness of his pupils, and he crooked his fingers, dragging his knuckles deliberately across a bundle of nerves inside of Cas that sparked a white hot trail straight to his cock as he pulled his fingers out.
A knowing smile curved at Dean's lips as he moved to position himself between Cas' legs, slicking his cock with a thick coating of lubricant. Cas brought his hands up, gripping at Dean's shoulders, one hand settling over the red handprint that he himself had marked there, an irrefutable reminder of the moment that had first brought them together. Dean gripped Cas' hips, angling them up as he pressed the head of his cock against Cas' entrance. He pushed inside slowly, keeping one hand on Cas' hip and bringing the other up to brace himself up beside Cas' neck. His head fell forward and his eyes closed tightly as a rough moan rumbled out from his chest.
Cas released a moan of his own, feeling every inch of Dean's length as it slipped inside him, stretching him open, filling him in the most perfect way. Dean stilled when he had pushed in completely, blinking his eyes open and looking down at Cas, wonder plain on his face. Cas could feel the hot throb of Dean's cock inside of him as they lay motionless.
"Is this okay?" Dean asked on an exhale.
Cas nodded brusquely, hooking his ankles at the small of Dean's back, urging him to move, to please God justmove.
And he did. Hesitant, shallow thrusts that soon morphed into rough pushes and pulls. The slap of skin on skin rang out in the confines of Cas' small bedroom, intermingling with the harsh and gasping intake of breath drawn from them both.
Cas could feel his orgasm nearing with each pounding move, and sensed Dean's nearing too, judging by his suddenly erratic thrusts. He angled his hips higher and felt Dean's cock glance over that bundle of nerves once, twice, and then he was coming undone with a hoarse shout, his cock releasing his spend onto his stomach in thick, liquid spurts.
Dean followed him over the edge almost simultaneously, crying out Cas' name in a broken stutter and filling him in a hot rush. He brought his head down to rest it on Cas' chest, fighting to catch his breath.
"I can't do it, Cas. This choice is too damn hard." He panted the words out, his breath washing over Cas' skin in warm surges.
Cas let his legs fall back to the bed gently and slowly pulled back from Dean, wincing slightly at the over-sensitization, and guided him to lie beside him on the bed. He pressed his hand to the handprint on Dean's arm and centered his gaze on him.
"I would never harm Sam. If nothing else, Dean, it is important you know that." Dean held his gaze, even as his eyebrows gathered together and harsh tears glittered at the corner of his eyes. As much as it hurt to be turned away, it hurt even more to see the pained confliction on Dean's face. Cas pulled Dean toward him as they lay on their sides facing each other, capturing his lips in a kiss, gathering him up in his arms and holding him tightly.
It did not take long for Dean to drift off to sleep, and it did not take long for Cas to make his choice for him, though it broke his heart in an irreparable way to do it.
He left the Men of Letters bunker before dawn broke the next morning, with nothing more than a toothbrush, two crumpled dollar bills, an angel blade, and the warming memory of a night he'd carry with him always.