Author's Note: This fic is written out of chronological order, but if you'd like to follow Dean and Cas's journey as it progressed linearly, I'll put a link on my profile to a tumblr post that lists the chapters in order. There will be some pairings outside of Dean/Cas, but there is no explicit material for those pairings. The fic is posted in full on AO3, but if you're willing to wait for updates here, I'll probably be posting once a week. Also, each chapter was originally written as a part on its own, so I'll be putting summaries up top in author's notes, like so:

The morning-after. Dean is a persuasive son-of-a-bitch when he wants to be.

I. The Mistake

The first sensation that Castiel picks up on as he slowly wakes up is soreness. His limbs feel completely loose and slightly achy, but in a pleasant way, like he's just had all the tenseness fucked out of him. He shifts a bit, and—yep, his ass is definitely sore.

It's been a while since he's had sex, and he really doesn't remember much of anything from last night—mostly just an alcohol-induced blur of talking and laughing and kissing and touching. God, it's really been so, so long since his last one-night-stand.

He becomes aware of warmth coming from a hard chest pressed against his back, a possessive hand curled around his hip. Ugh, this could get awkward. Castiel has always been good at keeping strings from forming, and staying the night is never a good sign. It hints at expectations. Another meet-up, or a proper date, or something. And Castiel isn't interested in a relationship, though he'll never admit the true reason why.

He lets out a soft sigh and shifts again, hoping that if the man behind him wakes up on his own, he'll realize that he's stayed too long and just leave—Castiel knows that this is his own bed.

It's surprisingly comfortable to relax back in the man's arms, and Castiel indulges himself for a few minutes as he waits for the stranger to wake.

The grip on his hip tightens slightly, and he feels the man behind him tensing up. So he's awake. Should be rolling out of bed, any second now…

Then the man behind him yawns loudly, and Castiel's thoughts shut down abruptly.

Shit, shit, shit, fuck.

"Mornin', Cas," the man—definitely not a stranger, because Castiel would recognize that voice anytime, anywhere—drawls lazily.

The half-hard cock pressed against the small of Castiel's back suddenly becomes impossible, too much, and the hand still resting on his hip feels restraining, terrifying. Because it's Dean fucking Winchester right behind him, hot breath curling around Castiel's ear as he lifts his head.

"D-Dean, what the fuck—" Castiel begins, starting to jerk away, but Dean's always been ridiculously strong, and Castiel realizes belatedly that he's lying on Dean's other arm, an arm that rapidly comes up in front of him, pressing him back into Dean's chest. The grip on Castiel's hip becomes bruising.

"Hey—hey—Cas, calm down," Dean's saying in a low voice, and if anything, this only makes Castiel thrash harder. He has the advantage of having been awake and alert longer than Dean, and he finally manages to twist out of Dean's hold.

He hesitates for a moment at the edge of the bed before Dean begins reaching for him, and he has to spring away. He instantly goes to his chest of drawers to find some clothes.

"Cas, what the hell?" Dean says from the bed. He's sitting up now, and Castiel sees red marks trailing down his chest, clearly left by fingernails. His fingernails. Fuck, fuck, fuck, Dean looks so deliciously debauched.

"Dean, I should be asking you that. How—why—I just—I don't even—how does one end up in bed, naked, with his very straight best friend?"

Dean grins. "Straight? After last night?"

"Okay, apparently bi," Castiel emends. He feels safer now in a pair of baggy sweats and holding onto a shirt, but Dean's marked-up torso is doing things to him. The small tent in the blankets right above Dean's groin isn't helping matters. "It was a mistake," Castiel says, dropping his eyes to the floor. "We were both drunk off our asses, and I hardly remember a thing—"

"Dude. Hey. If anyone should be making excuses like that, it's me. So shut up, man. You're not the one who just came outta the closet."

No, Dean doesn't understand. Castiel needs to rationalize this. Needs to categorize it in his mind as something other than feelings because he can't indulge himself when it comes to Dean. He's worked too hard on suppressing this to let it all go down the drain now.

"Cas—" Dean's voice comes from closer than Castiel's expecting it, and he looks up to see Dean coming right at him "—why are you flipping out?"

Castiel flinches at Dean's nearness and backs up, but he hits the wall far too soon, and Dean just crowds in, hands bracing the wall on either side of Castiel's head so that he can't escape. A quick glance down reveals that Dean's still undressed, and that his dick is still very much interested in the proceedings.

Castiel's mouth waters. Fuck.

"Dean, it was a bad idea. We can just… chalk it up to the alcohol, and pretend it never happened. Okay? I hardly remember any of it anyway, so—"

"Why?"

"Why? Because you're my best friend, and things are gonna get awkward if this—" Castiel gestures meaninglessly between himself and Dean "—keeps up. I don't want it to be awkward."

"Why would it have to be awkward?" Dean breathes, leaning in, and Castiel feels his eyelids fluttering instinctively, his heart rate increasing in response to Dean's nearness.

Castiel's lips part to answer Dean's question, but then Dean's tongue is in his mouth, chasing all capability of thought out of his head. They've both got morning breath and it's a bit gross, but Castiel can't even find it in himself to care, because Dean Winchester is kissing him.

Fuck, this can't be happening.

Dean's hands tug Castiel's shirt out of his hands, and Castiel shakes his head, breaking the kiss.

"Stop it," he says.

"I don't want to," Dean responds.

Castiel pushes at Dean's chest. "We have to stop. This… this'll change things. I don't want things to change."

"They don't have to. Cas—Cas," Dean says, catching both of Castiel's hands between his. "Stop fighting me."

Castiel lets his hands fall in surrender. He could never deny Dean.

"Look, I know you were pretty freaking smashed last night, but I wasn't that drunk. I remember enough to know that the sex was fucking animal, and that's not something I'm about to give up."

"So what, are we going to enter a sexual relationship just because you want to?"

"No, because we both want it," Dean says, hand reaching down to cup Castiel's half-hard dick through his sweats. "Don't you dare tell me you don't want it," he murmurs. "Nothing has to change, you know. We'll still be friends, just with a bit of fooling around on the side."

"What, friends with benefits?"

"Exactly!"

"That's—no," Castiel says. "That never works out."

"As though you have so much experience with it," Dean says.

Castiel tries to formulate a response, but Dean's hand slips beneath the waistband of his sweats, and he can't be blamed for forgetting what he was about to say. Castiel actually jerks when Dean's hand wraps around him, and he goes from half-mast to raging hard impossibly fast.

And then his sweats are being pulled down, and Dean's dropped to his knees in front of him. Castiel straightens, alarmed, and starts to protest, but then he's being engulfed by the hot, perfect warmth of Dean's mouth, and his brain short-circuits.

"Oh God—Dean—fuck—" he hisses, slumping back so that the wall can support some of his weight. He lets his hand drop to fist in Dean's short hair, all the while resisting the urge to just thrust.

For what could possibly be his first time giving a blowjob, Dean is fucking amazing—Castiel feels about two seconds away from coming, and he can't remember the last time he needed so goddamn much. Then again, it could just be because he's been repressing fantasies about this for too long, and actually having them play out is too much.

Dean pulls back slightly so that just the head is in his mouth, continuing to suckle gently, and Castiel moans helplessly. Dean tongues at the slit, and Castiel whines.

"Dean—Dean, I can't—" he babbles, and Dean pulls off wetly, licking his lips and grinning widely up at Castiel.

"You're so fucking pretty like this, you know that?" Dean murmurs as he regains his feet, crowding Castiel up against the wall.

Fuck it, Castiel thinks, and reaches out, hands grasping greedily at Dean's body, learning the planes of his back and chest, palming the globes of his ass. Dean grinds his hips forward, and the glide of their cocks against each other is too much and not enough all at once.

"Dean, I… I need…"

Dean chuckles, probably amused by the urgency of Castiel's tone, but thankfully he hoists Castiel's legs upward and settles in between them, and the feeling of having his dick sandwiched between their bellies, right up against Dean's, is fucking glorious.

Castiel wraps his arms around Dean's shoulders and fists a hand in Dean's hair, tugging his head backwards so that he can get a taste of Dean's throat. Then Dean's arm is gone from beneath Castiel's right leg, and he tightens his legs around Dean's waist, using the wall as leverage to keep himself in place.

Castiel tenses at the first press of a spit-slick finger to his hole, clenching instinctively, but apparently he was fucked thoroughly enough last night that his sphincter is relaxed and still a little slick, gives when Dean really starts to push.

"Dean—" he gasps, voice choked off, and Dean silences him with a kiss.

But Castiel doesn't want this, can't want this, he tells himself, even as his hips shift backward to take more of Dean's finger.

"See?" Dean says, voice only just louder than a whisper. "Knew you wanted it."

And Castiel gives up, gives in, stops trying to pretend that this isn't happening. The damage's already been done, so why not take what little of Dean he can get, while he has the chance?

But he knows exactly why not. Because if they really enter into a sexual relationship, he's going to feel hopeful for something more, and that won't do. Castiel doesn't want to be hurt, but hell, he's already hurt.

He reaches a hand down and wraps it around Dean's dick, giving him a firm stroke, root-to-tip. Dean lets out an obscene moan and sinks his teeth into the junction of Castiel's neck and shoulder.

"Fuck, Cas… what you do to me."

Dean adds a second finger to join the first, and Castiel times his strokes with the rhythm of Dean's thrusts. And then Dean's fingers find his prostate, and his hand falters, body seizes up.

"Oh fuck—Dean—" he groans, and he doesn't think he's ever heard his voice drop so low before.

"I got you, Cas, I got you," Dean says, and Castiel wonders how their roles got so reversed. If anything, Castiel should be the one talking Dean through this, seeing as he's the one who's more experienced with gay sex.

But this is Dean, so it's no wonder that Castiel feels helpless, overwhelmed.

Dean's trembling a little with the strain of keeping Castiel up against the wall, so Castiel flattens his hands on Dean's chest and pushes, leaning forward to kiss him so he understands that this isn't over yet.

They tumble back into Castiel's small bed, and Castiel loves the warm, heavy weight of Dean settling over him just a little too much. He's so fucked.

"Dean, we need to—" his voice hitches as Dean's fingers press inside again, three instead of two this time, but then he continues, "—to talk."

Dean's eyes fix on Castiel's, and his pupils are blown wide, dark with want. His voice comes out in a frustrated growl. "Now, of all fuckin' times, Cas?"

His fingers thrust in hard, pressing insistently on Castiel's prostate, and Castiel arches up, throwing his head back against the pillow. Goddamn, it really has been too long.

"You want me to talk, Cas?" Dean says, a dark glint in his eye, and he jabs Castiel's prostate again. "Yeah, I'll talk. Ben's birthday party, remember that?"

Castiel tries to respond, but Dean's fingers haven't let up yet, and all Castiel gets out is a pathetic whine.

"You caught me starin', asked what was wrong. I'll tell you what was wrong." His voice lowers to a nearly a whisper as he continues, "I wanted to shove you, bend you down right over the dining table, and fuck you. Right then and there, kids and cake bedamned."

Castiel gasps at the visual, at the flash of guilty heat that comes with it, and he needs, needs—

"S'ok, Cas, don't worry. Gonna give it to ya," Dean says, and it registers with Castiel a moment later that he must have said something aloud.

Then Dean's lips press against Castiel's, and he opens his mouth instantly, one hand fisting in Dean's hair, the other gripping his shoulder. Castiel surrenders, lets the taste, smell, feel of Dean take him over.

An indeterminable amount of time later, Dean's pulling his fingers out, lining himself up, and pressing in. And even after whatever happened between them last night, it still burns to be stretched this wide, but fuck does it feel good.

Dean groans in a gravelly tone as he sinks in. "If I didn't know any better, I'd say you were a virgin," he grunts. "So—fucking—tight—"

The last three words are punctuated with three rough thrusts, and Castiel's voice jumps up to a reedy whine. His hands scrabble at Dean's shoulder blades, nails adding to the crisscrossing of scoring already there, and Dean hisses, hips moving faster.

But his thrusts aren't hitting the spot, and given his perfect aim with his fingers, he knows where it is and is intentionally avoiding it. Castiel usually tops, doesn't bottom unless his partner gets the better of him. He isn't a person who begs—that's just not in his nature. Yet Dean's already gotten him to do it more than once, and judging by his actions now, he's angling to get Castiel begging again.

And Castiel would be upset or insulted, except that Dean's screwing deep into him but not deep enough, and he craves it so badly that he thinks he might die.

"Dean—Dean, please—"

Dean chuckles, low and rough, and the sound of it echoes in Castiel's head, curling around his mind like thick smoke. Still Dean doesn't change the angle, and any adjusting Castiel attempts to accomplish himself is foiled by Dean's firm grip on his hips.

In retaliation, Castiel waits until the next time Dean's seated fully inside him before clenching down hard, startling a moan out of him. Dean's whole body seizes up, and for a moment, Castiel thinks the game's up. But then Dean's slowly pulling out again, still thick and hard.

"Cas, you fucker," he breathes, and Castiel just looks up at him innocently—well, as innocently as one can look while stuffed full of cock.

When Dean sinks back in, Castiel repeats the motion, and Dean groans.

"Jesus fuck—what are you?"

Dean's next thrust jars his prostate, and Castiel chokes on a gasp. Dean gives him no time to recover, picking up the pace of his hips and hitting that sweet spot every time.

Castiel's not a virgin—far from it, in fact—and he's certainly bottomed before, but it's never felt like this, this raw, bordering-on-painful buildup of pleasure, this fucking scary sense of completeness whenever Dean slides home inside him, and Castiel lifts his head, kissing his way along Dean's jaw, throat, whatever he can reach—anything to keep him from saying something stupid, from spewing out the mantra of I love you I love you I love you that's cycling through his head.

Dean starts to lose control over his rhythm, but his aim somehow stays perfect, and Castiel's mouth starts running.

"Come on, Dean, do it—fuck, harder—" and he's interrupted by a sharp thrust that forces the air out of his lungs "—yes, just like th—hnngh, fill me up, Dean—need it, I need—"

He gives up on speech and settles for wordless moans, the pressure inside him winding up higher and higher with each forward snap of Dean's hips. He's right there, right on the verge of fucking bliss, and he just needs one—two—

Dean thrusts in roughly and comes to a halt, cock pressing insistently on Castiel's prostate, and Castiel can't do much more than cry out at the stimulation. Dean's hips roll in small motions, relentlessly, and Castiel feels stripped to the core, inside-out and raw. It's too much. His fingernails dig into Dean's shoulders, his back arches, and thick stripes of come paint both their torsos as he finally topples over the edge.

Through the haze of his orgasm, Castiel's barely aware of Dean snapping back into motion, lasting maybe half a dozen frenzied thrusts before finally stilling, face slack with pleasure as he comes.

Dean collapses over him, boneless, and Castiel's too comfortable to even ask him to move. It's quiet for a while as they wait to catch their breath, and Dean eventually shifts slightly to the side to take some weight off Castiel.

"I have office hours today," Castiel says, groaning. It's Sunday. Why is it Sunday?

Dean just grunts and lifts one shoulder in a half-assed shrug.

"Get off me, Dean. I've gotta shower."

When Dean doesn't respond, Castiel sighs and tries to slip out from beneath him, but a large hand clenches on Castiel's hip, holding him close.

"Dean," Castiel says impatiently.

"Hmm, fine," Dean grumbles, fingers uncurling from their positions around Castiel's hip.

Castiel slips out of bed and makes a mental note to throw the sheets in the laundry when he gets home.

Castiel comes out of the shower and finds Dean right where he left him—lying blissed-out on the bed. Feeling exposed, he turns to his dresser to pull out some clothes and puts on a pair of boxers.

"Cas… this isn't gonna be awkward now, is it?" Dean asks from behind him.

"I don't know," Castiel responds, pulling a t-shirt over his head. He hears shifting and turns to see Dean getting off the bed—still naked what the hell—and moving toward him. He lets Dean crowd him back against the dresser, lets Dean's hand rest on his cheek for a moment.

"Tell me we're doing that again," Dean says.

"I don't know, Dean."

"Well, it's not like we can just forget this ever happened." Dean's hand slips down to Castiel's neck, thumb rubbing his skin gently, and Castiel realizes that he's tracing the hickey he left there. "Hell, Cas, I see this on your neck, and it just makes me wanna mark up the other side, too."

"Don't."

"You can't say you don't wanna do this again. Come on, Cas."

"It'd be better if we didn't. Sex complicates relationships."

"Well, how 'bout if we set up some ground rules to keep things simple?"

"You can't just—"

"Sure I can. C'mon, Cas, work with me here. Or am I that bad of a lay?"

Castiel gives Dean an annoyed look. "Fine. What sort of 'rules' are you suggesting?"

"Um. I don't know, anything that keeps strings from forming?"

Castiel sighs wearily and turns away to pull on a pair of jeans. "Dean, we're friends. There are already strings."

"Oh, you know what I mean. Emotional stuff."

"Dean, I don't know about this." But he's never been able to actually deny Dean completely, so when Dean opens his mouth to keep arguing, Castiel surrenders. "No cuddling," he says.

Dean stares at him. "Dude."

"Cuddling fosters closeness. If we're avoiding a serious relationship, we can't be cuddling."

"Dude, you know what Anna's said about me. You can't—"

"What? What has Anna said about you?" Castiel teases, turning to grin at Dean.

"Oh, fuck you."

Castiel clears his throat. "Think that's already gone down, cuddleslut."

"Yeah, yeah, laugh it up. If you're gonna take my cuddles away, I won't make breakfast for you in the mornings."

"You shouldn't do that anyway. It's usually taken to be a romantic gesture."

"Okay, how 'bout we make the rule 'no staying overnight' instead. I mean, come on. It's practically impossible to not cuddle after sex."

"For you," Castiel says. But Dean fucking pouts at him, so Castiel has no choice but to concede, "Fine." He gets this feeling in his gut that he shouldn't be doing any of this in the first place, but he's always been unfortunately adept at ignoring that feeling when it comes to Dean.

"Okay uh, we shouldn't be exclusive, yeah?" Dean says. "If either of us meets someone, we can just call this off."

Castiel nods, doing his best to ignore the pang in his chest. Then Dean smiles, and Castiel can only look at him for a moment before averting his eyes. How could anyone not love this man?

"We should probably keep this low-profile," Dean says, and Castiel shrugs.

"Why should we? It isn't as though we're doing anything wrong."

Dean hesitates before nodding. "Yeah. Yeah, you're right. Doesn't matter what other people think."

Castiel returns his smile before reminding Dean, "I've gotta head out. Office hours."

"Right. Sunday."

"Yep. I'll see you later, all right?"

"Yeah."

Castiel walks out of his bedroom and across the small living room to the door of his apartment. "Lock the door on your way out, 'kay?" he calls as he pulls on a pair of shoes.

"Got it!"

Castiel exits the apartment, closes and locks the door behind him, and just stands there for a minute. Fuck, this has gotta be the worst mistake he's ever made in his life.