Alright, I know I told people that I wasn't doing fanfiction this month because I was doing NaNoWriMo (an event where you wrtie a 50 000 word novel in the month of November) and that if I did take a break from my book, it would be to finish up the last chapter of "Two In One".

However, me being the stupid person that I am, I somehow managed to get myself obsessed, absolutely obsessed with a pairing that never became canon from a tv show that ended. Only I would be that dumb, I swear. Frankly, my new love of Dasey is distracting me from my NaNo book, which is bad, so I thought I'd write some fanfiction to get it out of my system.

This takes place directly after the finale episode of season 4, and uses some lines directly from that episode. I own nothing. This is rated T, but it's a strong T, bordering on M. Be mature.

Derek Venturi did not "do" emotions.

Like, at all. They just ruined everything fun, and made you look like a sap. Uh, no thanks to that.

If he had to pick one thing he loved to do, it would be messing with Casey. His step-sister was hilarious when she was pissed off. Sometimes her face would pop into his head at the strangest of times: that expression of livid anger she got when he had done something particularly evil, that purse of her lips right before she shouted his name in utter fury.

"De-REK!"

God, he loved hearing that. Yep, messing with Casey would never get old, because he loved seeing her reactions.

Damn, he was getting off topic. That tended to happen to him a lot when he thought of Casey, not that he tried to think of her a lot (unless he was pranking her) because she was, of course, the bane of his existence.

But yeah. That whole "feelings" shtick was not for him.

That's why this was freaking him out.

He'd just come down to the kitchen to eat some cereal while he read over the courses he could take. The fact that it was the middle of the night didn't stop him (hell, the middle of the night was obviously the best time to eat cereal). And then Casey came in.

So they talked a little. Might as well, because she was there. It was slightly weird, because they weren't really arguing, but then again, they had been arguing less and less as time went on. In fact, he could've sworn sometimes that she liked talking to him.

Had to be his imagination.

"Do me a favour," Casey said, tilting her chin up. "When you see me in the quad, pretend you don't know me."

He smirked. What, did she think she was getting rid of him that easily? Hell no: he'd been irritated only for about one minute when he realized that they were going to the same university, and then he'd suddenly seen the bright side in it. Maybe when she had reached over during that family hug thing and ruffled his hair she'd knocked some ideas into his head.

Now he could bug her even more, and without parents around it would be twice as fun. He could come to her dorm and meet her hot roommates and maybe coerce Casey into helping him test out the durability of her bed—

He quickly pulled his thoughts out of whatever fucked-up weird place they'd gone to and shoved them back into the conversation.

"Are you kidding?" he replied, leaning forward slightly. "We are going to be best buds and then you can introduce me to all of your sorority sisters."

Sorority sisters, yep. Hot sorority sisters. This was definitely a safe topic. Hot girls and Derek Venturi went together like chocolate syrup and ice cream.

Casey shook her head, but he thought he saw the glimpse of a smile at the corner of her mouth.

"Derek, you are the most annoying brother—"

And there went his good mood. That word always felt like a sucker punch to his stomach when she said it referring to him.

"STEP," he corrected, the grin falling from his face. "Brother."

There was a damn important distinction there. Derek Venturi was not related to Casey McDonald, and she needed to know that.

She hesitated slightly, her eyes meeting his. He really wished she was standing somewhere else, because as it was, her eyes were really distracting and sort of...sparkly in the light.

"Same difference," she said softly, but she was watching him, almost as if she was looking for his reaction.

He had the feeling that he should look away, that he'd been looking at her for too long. Same difference? Bullshit. There was a huge difference, and it had everything to do with the fact that he couldn't look away from her.

"Yeah," he said, and fuck, his voice sounded gravelly and sort of pissed and did not come off with the "whatever" tone of voice he was going for at all. "Alright..."

Again with the staring. She did some distracting little twitchy smile with her mouth and his eyes flicked down for less than a fraction of a second before they focus on her eyes once more. Except eyes were not safe territory because he'd been staring at her way too long and she was going to get suspicious and he needed to change the topic NOW.

"Hey," he said, dipping his head and desperately trying to regain that teasing tone he'd had earlier. "Maybe we can live in the same residence."

And suddenly they were back on equal footing. He was joking around and she was joking back, and he was just starting to get comfortable (as comfortable as you can get when you're talking to Casey) when she started mentioning going out with frat boys.

"Oh no! You are not dating my fraternity brothers!"

Him dating her sorority sisters was perfectly fine, because hey, he was Derek Venturi. There was no way in hell though that she would go anywhere near his friends in university. He'd had enough of that shit during the whole "Sam" faze that she'd gone through. That had been awful. There was definitely not going to be a repeat of that.

"And why not?" she said, placing her hands on her hips. He was starting to wish that she hadn't come around the kitchen island to his side. He was starting to wish that she hadn't come downstairs at all. "You get to have fun, but I can't?"

He snorted, resisting his instinctive urge to move away. He would not give in to a girl, damn it!

"You're Casey," he retorted. "You don't know the meaning of fun. And no," he continued as she opened her mouth to reject his words. "real fun does not involved flash cards or educational games."

She narrowed her eyes, and his grin widened. Definitely nothing funner than messing with Casey.

But then her smile drooped and she turned away, setting her course book on the counter and moving towards the living room. Derek stared after her, following without even really knowing why. She couldn't just walk off, not while he was talking to her!

Casey wandered over to a side table and picked up a picture frame lying there. Derek came up behind her, peering over her shoulder and trying not to get distracted by the heat of her body radiating from her. It was dark, only a few lamps lighting the way, but even in the shadows he could see that it was a family photo, one of all of them together in the shot. He couldn't help but smirk at Smarti, sitting on Casey's lap and grinning out at the world.

Then he heard a sniffle.

Derek froze, turning his head to look at the girl holding the photo. Please say that wasn't...

"It's just..." she said slowly, tears choking her words. "It's just that I'm going to miss everyone."

Oh god. She really was crying. Derek stepped away from her, automatically raising his hands for protection. He hated crying. He hated it especially when girls did it, because he had no idea what he was supposed to do.

"Uh, can you not do that?" he said uneasily. Her shoulders were starting to shake. Where had this even come from? One second she was all "let's have flirtatious conversation about university" and now she was bawling her eyes out over a picture? What the hell was wrong with women?

Casey whirled on him, and he was alarmed to see that there were actual tears streaking down her face.

"Look," she hissed, advancing on him. "I'm just sad that we'll be leaving everyone! Aren't you going to miss them a little bit?"

He staggered even farther backwards. His knees hit the couch and he scrambled onto it, sinking into the corner defensively.

"Sure, I am," he said tentatively. That was the truth. He was going to miss all of them...but only a tiny bit. Like, less than a molecule. Less than whatever was smaller than a molecule.

He really wanted her to stop crying. It hit him that this was the perfect time to flee: abandon the cereal he'd left in the kitchen and just book it upstairs. But it was like she was paralysing him there with her red eyes and he could not move. If he hated crying, he especially hated when Casey cried. There was something about seeing her like that that made his chest clench up and—god damnit, Derek Venturi did not do this feelings shit.

Maybe it was because he was too preoccupied with arguing in his head, but despite his hockey reflexes, he didn't move in time to avoid what happened next.

Casey crawled onto the couch and flung her arms around him in a hug.

There was a reason that Derek did not let Casey hug him. It wasn't so much that he didn't want her to touch him—hell, his hands found themselves on her shoulders and waist and stomach 90% of the time while they were fighting anyway, without his permission—but a hug was full on. It was front to front, arms around each other. It was way too much, and he'd always had this strange feeling that if he and Casey were ever to hug, something monumentally bad would happen.

Frozen? No, he had petrified, as in turned into STONE. There was no moving him now. Struggling would be useless. She had a vice-like grip on him, and he was going nowhere fast. He could barely think, because she was inbetween his legs and sort of straddling him and her head was against his chest, tucked right under his chin.

Holy shit.

"Knew I could catch you eventually," she muttered, and he almost relaxed, because it was a joke, but then she continued, her voice growing sad and teary again. "It's just a little nice to know that you're going to Queens too, because then at least I have some sort of link to home there, you know?"

Derek was resisting several things at that moment, the foremost being the urge to just put his arms around her, followed closely by the urge to kick her in the gut and run.

"Weird thing to say to someone you hate," he said quietly. He meant it to come out as a joke, but somehow it just made him sound vulnerable, and he wanted to punch something.

"I don't hate you."

And he couldn't help it. His arms came back to life and swept around her, pulling her against him. His body curved forward, shifting her more comfortably, and he let her cry into his shirt.

There had to be something wrong with him. This was not natural, no matter how easy it felt. He liked to screw around with her, not hold her like he was her personal teddy bear, or boyfriend or something!

His instincts about hugs had been right: they were damn dangerous things. Just having her this close was bringing to mind everything he'd subconsciously tried to suppress for longer than he even knew. Like how much he liked the press of her body on his, the tickle of her fingers at the base of his neck. He'd thought about what that would feel like before, only to shove it away. And the way her hair smelled like some fruity stuff that was...awesome. He'd accidentally used her shampoo once and the whole day had been weird because he had gone around smelling like Casey and feeling jumpy for no reason. And now all the emotions he had concerning Casey were starting to tumble out like an avalanche and that was bad, that was beyond bad, because he couldn't—

She shifted slightly in his lap and he hissed, feeling her hips rock into his. They both stiffened, and he remembered with slight hysteria that there were things worse than having "feelings".

Things like getting a boner when your step-sister was in your lap.

Her breath was still huffing out against his neck, but he didn't dare to breath at all. Maybe if he stayed still enough, she might think he had died and the thing in his pants was just a weird result of rigor-mortis. Because, even for the lord of lies, a good excuse was just not coming to him right now.

She pulled back just enough to look up into his face.

Derek didn't know what he looked like—though panic was a good estimate—but her face was impossible to read. Her mouth was slightly open, and there were still tear tracks on her skin, the wetness making the dim lamp light glimmer in her eyes. She blinked once, long lashes swooping down to brush against her cheeks, and the tip of her tongue darted out to lick her bottom lip.

Fuck it.

He didn't really know how it happened, but there was no way to stop it. One second he was just looking at her, waiting for her to leap away and scream something about castrating him, and the next second his hands were tangled in her hair and he was crushing his mouth to hers.

He was kissing her.

She gasped when his lips touched hers and he took advantage of that open mouth, snaking his tongue inside. Her body arched into his and he felt her hands spasm against his back. It took him a moment to realize that she was kissing him back, moving her mouth with his, and that realization took what little breath he had left.

Derek tore his mouth away and got one glimpse of her hazy eyes before he was closing his again and moving back in to the kiss. Somehow he had flipped them over—he had no memory of doing that—and he pressed her down into the couch, flattening his body against hers. It was like fire. It was like fire everywhere and he couldn't stop. Was this wrong? He had a distant feeling that something about this was wrong, that there was a reason he shouldn't be doing this, but he couldn't remember it at all. He didn't want to remember it.

Her dancer's legs were twisting around his and their hips were instinctively moving against each other, rubbing, grinding. Derek tried to remember how he'd always calmed himself down before when he had been with other girls, but nothing was coming to mind. Casey's touch—her hands sliding under his shirt and threading through his hair and clutching his arms—was erasing any powers of thought he'd ever had. All he could do was helplessly thrust against her, listening to her breathing hitch and stutter with his every movement.

He broke away from her lips and trailed his mouth down her jaw to her neck, sucking on the skin over her pulse. She liked that: her head tipped back, her heartbeat hammering. She tugged at the bottom of his shirt and he pulled away from her just long enough to yank it over his head, throwing it away before reattaching his face to her collarbone. Derek had wanted this for so long. Denial meant nothing now. He loved to mess with Casey, and he had loved that only because he hadn't been able to do this to her.

He sunk his teeth slightly into her shoulder, his hands slipping under her shirt to trace the undersides of her breasts—she wasn't wearing a bra, a fact that made him even more turned on. Casey started at his touch, her legs tightening around him, and he heard his name leak from her mouth, a half-whisper, half-moan.

"Der-EK..."

Oh fuck, he definitely had a new favourite way to make her say his name.

Even with his brain all hazy, he could tell where this was going. They were moving together faster now, desperately, and if they didn't get these clothes off soon, then he would be making a mess in his pyjama pants.

He moved his mouth to her ear, licking over her earlobe.

"My room or yours?" he panted.

And she stopped moving.

She simply ceased all movement. It took him a second to realize it, and he drew his body back from her slightly, propping himself up on his arms to gaze down at her.

She was staring up at him, her eyes huge in the darkness, and her expression scared him so much that he could barely breath.

"You're my step-brother," she choked out. "You're Derek. I...I can't—"

And she was scrambling out from underneath him, frantically untangling herself. Sobs of breath punched their way out of her mouth and he grabbed her wrist just as she got to her feet.

"Case—"

But what the hell was he supposed to say? How could he explain something he didn't understand?

"This—this didn't happen, okay?" she pleaded.

He gaped. So she was just going to pretend that this was nothing? That they were a happy little family? That she hadn't just made out and almost had sex with her step-brother on the couch? Fury rose in him, unlike anything he'd ever felt before, and he snatched his hand back from her like he'd been burned.

"Fine," he snarled, his mouth twisting up into a smirk. "Go on then, Princess. I was just playing with you anyway."

For a split second she didn't move, but then she dashed for the stairs, tripping over herself and running up the steps as fast as she could. Her shoulders were hunching and her hand was over her mouth, but for once in his life, Derek didn't care that she was crying.

Because he was hurt. Because he wanted to punch the shit out of something. Because he wanted to fuck her, but—even more than that—he wanted to make love to her.

Derek Venturi did not "do" emotions.

Derek Venturi liked messing his step-sister and pranking her. He liked laughing at other people's failures and he liked picking up girls and going through them like a deck of cards.

Derek Venturi was not in love with Casey McDonald.

So who the hell was he now?

THIS IS A ONE SHOT. I know it's not written like one, and leaves on a sort of cliff-hangery moment, but I'm not going to continue this. I...like it the way it is.