A/N: My first ever oneshot. This is for all the dasey fans who want a dasey type ending to LWD!

Disclaimer: i do not own Life with Derek otherwise this would actually happen!

Party Fever!

It was the night after their graduation ceremony and there was going to be a party. It was to be thrown by Ralph who was so excited; he almost forgot to go to graduation at all. Casey was to arrive with her boyfriend Truman, and Derek was to arrive with his girlfriend Emily.

Derek and Emily arrived first out of the two couples and Emily dragged Derek to the dance floor almost immediately.

When Truman and Casey arrived shortly after, Truman said that he wanted to go find some of his friends. Casey objected and asked nervously if he wanted to dance first. He smiled at her and assured her they had all night to dance, then giving her a quick kiss on the cheek, he walked into the ever-growing crowd of teenagers to find his friends.

Casey sighed quietly and remembered the last time Truman had left her alone at a party. She removed her coat and sat on the many chairs that faced towards the centre of the living room that was currently being used as a dance floor. She watched as Derek and Emily danced closely in the swarm of bodies that surrounded them. After a moment Derek noticed Casey out the corner of his eye and saw that she was alone. Casey lifted her head slightly to once again stare at the dancers and she caught Derek's gaze. Before turning away swiftly, Derek and Casey both thought the same thing; 'What is Truman up to now?'

After thirty minutes of dancing Derek was slowly starting to get frustrated. He was always constantly making-out with Emily ever since they had started dating and so he had forgotten how much she liked to talk. Every now and then his mind would wonder from the mindless gossip Emily was spouting and stared over at Casey. Four different guys had asked Casey to dance in the last half hour. Casey had sadly turned each of them down as she didn't want Truman to get the wrong impression. Derek thought this was stupid as he was willing to bet that Truman was off somewhere chatting up another girl, or maybe worse. Casey's petit face was hanging slightly low and was staring longingly at the dancers, the corners of her mouth were turned down and her eyes were sad. Derek hated seeing her like that.

On the other hand, he loved seeing Casey annoyed, especially when it was because of him. This was because he loved how she looked when she scrunched her nose in anger and her cheeks would flush scarlet; it was such a cute sight.

'Wait!' Derek suddenly stopped dancing at the thought. Did he just think of Casey as cute? He shook his head at the notion and then noticed Emily had stopped talking and was staring up at him curiously.

"Derek, what's wrong? Why have you stopped dancing?" Emily asked as she tried to talk over the loud music.

Derek thought quickly, being the lord of lies helped him think of an excuse speedily.

"I was just planning on going to get us some drinks, you want one?"

Emily smiled satisfied with Derek's excuse and said she would love a vodka and coke. "Oh and could you please take Casey to get a drink, it looks as though Truman's ditched her again and she's going to need some alcohol in her system if she's going to survive the rest of the night." Derek nodded and then walked towards Casey. He thought for a moment and wondered why Emily hadn't asked Casey to dance with them or at least spoke to her if she knew she was all alone.

Casey looked away from the dancers and stared up at Derek with wide eyes. 'What did he want? Surely he doesn't care she's sitting alone,' she had actually been waiting for Emily to come over.

I'm going to get some drinks, you want to come with?" asked Derek guardedly, he didn't want Casey to start poking fun at him for having a heart and caring that she was alone.

Casey debated in her head whether or not to go with Derek. She didn't normally like to drink, but she knew she was just going to be feeling shitty for the rest of the day if she didn't start enjoying herself soon.

She followed Derek into the kitchen and they stood by the kitchen table waiting till other kids were done so that they could have access to the booze.

Derek felt awkward as the silence between him and Casey stretched on. He was use to them always arguing or at least talking.

"So where's Truman?" Derek attempted conversation, even though he knew the topic wasn't the best one to start off with.

Casey shrugged her shoulders as if she really couldn't care less. "Around I guess, he said he went to go find his friends." Derek heard the stress she placed on the word 'said'.

"Well I'm a little surprised you didn't just dance with the guys who asked you earlier," Derek said as the alcohol finally freed up and Derek started pouring three cups of vodka.

"Well I said no out of respect for Truman, but now I feel like saying 'screw him' and dancing on my own," she said as she got comfortable by sitting on the kitchen table were Derek was pouring the drinks.

"Well why don't you?" Chuckled Derek as he looked to his side and noticed his face was incredibly close with Casey's hip. It was then that he finally noticed what she was wearing. She had her hair down in loose curls and she was wearing a short, silky lilac dress that stopped just slightly below her thigh and clung to her every curve. Derek also noticed how the dress was revealing more skin then necessary on her thigh now that she was sitting. Casey on the other hand didn't seem to notice as she was now swallowing down the contents of one of the plastic cups Derek had poured. Derek stared at her sheepishly while adding "Err, I haven't put the coke in that yet."

Casey waved her hand In front of his face as she removed the cup from her lips. "Ah, it would only slow down the effect."

Derek couldn't help but smile widely, shaking his head as he made up more drinks. Sometimes he didn't get Casey. One moment she would be her super-keener self, all for rules and what not, then the next she would be happy, rebellious and down-right fun to be with!

"So what about you and Emily? You to seem to be having fun," said Casey before taking another large gulp of her drink.

Derek also took a generous swig of his drink, using it to avoid answering the question.

He removed the cup from his lips but continued to stare at it as he spoke.

"It's ok I guess. Problem is, I only seem to really enjoy the whole relationship when we're on physical terms," he explained carefully, not wanting Casey to start yelling at him about her best friend.

"Derek Venturi, what have you been up to with my best friend?" asked Casey jokingly as she smiled at his obvious caution in his voice. She knew they hadn't really been up to anything like that, because if they had had sex she would be hearing it from Emily non-stop.

Derek rolled his eyes playfully at her mocking appearance. "Hey its' not me you should be worried about."

Casey lowered her cup that she had just finished and stared at him cautiously. "Do you mean Truman?"

Derek looked surprised and quickly reassured her. "Actually I was talking about how Emily keeps trying to jump me every second we're alone."

Casey snorted at this confession as she reached for another cup of pure vodka and began gulping it down again.

Derek stared at her drinking for a while before asking, "Should I be worried about Truman." Casey lowered her cup slightly so that she could look over the top and contemplated how to answer. She didn't have to worry though because at that moment Emily came staggering through, asking what was taking so long with the drinks. She then saw Casey sway ever so slightly from where she sat on the kitchen table,

"Oh now I see; you've been drinking them all."

Derek looked at Casey and saw that she was staring at him, while trying to stifle a giggle at the look on Emily's face. Seeing Casey biting her lip to prevent her from laughing made him want to laugh too, and soon they set each other off in an unfamiliar but enjoyable laughing fest. Emily rolled her eyes. "How could you guys get drunk with out me, that's not fair," huffed Emily as she crossed her arms in annoyance. This only made Casey laugh harder. Derek stumbled over to Emily and gave her arm a squeeze while handing her a cup, offering her to catch up.

"Actually I think I'm gonna head home, I'm not feeling all that great," she said pushing the cup away from her. "But please stay here and have fun!" said Emily sarcastically. Derek not catching on that she was joking, said ok, wished that she would feel better soon and returned to Casey's side, downing the drink he had offered Emily in one gulp. Casey shouted out her farewell to Emily as she stomped from the kitchen and out the front door.

"So I guess it's just you and me then until Truman returns from wonderland," said Casey as she carefully hoped off the table. Derek noticed the dress slip further up as she slid off and he got a got look at a black thong Casey was wearing, obviously for Truman's benefit. Derek nodded in agreement to Casey's statement and then they both looked at each other and knew exactly what the other was thinking. They grabbed as many bottles of alcohol and shot glasses they could find and then moved their party of two into the more comfortable atmosphere of the sitting room and onto the couch.

They both did a shot each before they picked up the conversation again.

"Ok, so I know you haven't had sex with Emily yet, but have you done it at all?" asked Casey as she began pouring out another shot for herself.

Derek stared at her with his eyes wide and his cheeks beginning to turn red. "That's a bit of a personal question don't you think, Miss McDonald?" he said jokingly. It wasn't like Casey to ask such personal questions, especially not of him.

Casey smirked at him mischievously. "What can I say, I'm curious whether all those rumours around school are true." Casey downed her shot followed shortly by Derek with his.

Derek stared at her as though she should already know the answer to her question. "I've heard those rumours. I must sound like a right man slut; apparently I've slept with every girl I've dated since the eighth grade," he laughed at the stupidity of it all.

"And you were fantastic too, apparently," Casey joined in the laughter as she started to become very unsteady on the couch from the amount of drinks she had consumed. Derek could handle his alcohol a lot better then Casey, but even he appeared to be swaying shakily on his seat.

"Well, Sally can vouch for that," he said smugly as he watched Casey's reaction from the corner of his eye. Casey's eyes widened and her mouth dropped open at Derek's statement. Her lips twitched into a grin as she spoke.

"You and Sally slept together?!" she knew she shouldn't be surprised, but she was.

"Yeah, but I'll let you in on a little secret…" he said as he leaned in closer to Casey so as to whisper in her ear. Casey could smell the alcohol on his breath but it was soon masked by her own.

"I've only ever slept with sally," Derek's cheeks flushed with embarrassment at what he said and so picked up another glass, and threw the contents back so as to hide his face.

Casey saw him cringe at his confession and so smiled at him reassuringly. "Well I've never done it with anyone so I win!" she threw her arms up in the air carelessly, and the drink she was holding splashed down on both of them. They both burst out laughing and ignored the two confessions that they had both just made.

Casey and Derek both noticed how the party had died down considerably now. People had either gone home, moved on to somewhere else, or made their way upstairs for some privacy.

"Well I can't say I'm disappointed Truman hasn't violated you," Derek said jokingly, although part of him was deadly serious.

Casey smirked at him. "I said we hadn't had sex, I didn't say we had never done other stuff," she wiggled her eyes suggestively at Derek and her words came out slightly slurred, but Derek heard every word clearly.

He stared at her, trying to figure out from her smirk, whether she was being serious or not. "No way has he touched you like that," he said trying to keep his voice light, but the unmistakeable sound of disgust could be heard in his voice.

Casey chuckled to herself. "Derek, you sound like a jealous boyfriend," she laughed again in amusement at her own accusation.

Derek tutted at this and turned his head in the other direction.

Still laughing Casey leaned forward and copied Derek's earlier posture by whispering in his ear. "Derek's jealous!"

"Whatever," he said as he tried to ignore the feeling of Casey's warm breath on his ear.

Casey shifted her body so she was somewhat more in front of him now. "Derek wants me all to himself," she said tauntingly as she stroked a finger down his left cheek, which he batted away quickly. She then stood up and stood in front of him. Derek turned his face to stare at her in amusement. Her face was bright and lively and he could tell she was having a lot of fun teasing him.

"Derek lusts after me," she said, her voice becoming quieter now. Derek shook his head slightly and rolled his eyes at her playfulness.

Casey then lowered herself onto Derek and straddled his lap, her dress sliding very high up her toned thighs. Derek tried to keep his hands planted at his side, but he couldn't help but stare at Casey's face with a big smile at how far she was willing to go to torture him. He really liked her when she was drunk.

"Derek wants to feel… my body," Casey sighed seductively. She wasn't wrong. He did want to feel her body, especially right now and he was having particular trouble resisting. Unfortunately he knew she was joking and they were both drunk so it wouldn't be right to take advantage.

Casey learned her head down so low, that Derek could have sworn she was going to kiss him. Then she whispered barely audible, "Violate me, Derek!"

This made him want to laugh so hard and so he decided to return the favour. He shifted their bodies so that she was now lying on the couch and he was leaning in between her legs and he began tickling her like crazy.

They both laughed till their cheeks hurt, until Casey finally screamed her surrender. Both out of breathe and still pumped with adrenaline to move, Derek looked down from his position and into Casey's eyes, while she did the same.

Casey looked up at Derek and saw his face was red from the fight as she was sure hers was. She lifted her index finger and mimicked her movement earlier. She stroked it slowly and gently down Derek's temple, across his cheek and down to the end of his chin. Although she had done it earlier, this move was now incredibly intimate.

They stared at each other for what felt like hours, neither daring to move. Eventually Casey felt her body lift slightly on its own and her lips crashed onto Derek's.

Derek's mind was screaming that this was wrong. She was drunk and she was his step-sister. But the feel of her soft lips moving against his, knocked all his inhabitations out.

The first kiss was gentle and careful, as though testing the waters to see if either one of them would object. When neither did, their kisses consisted of sloppy drunken smooches and groping.

Derek's hands slid down to her hips and his fingers teased the skin that was exposed at the bottom of her dress. Casey's hands stroked through Derek's hair as she felt him press himself into her body. Casey let out a soft involuntary moan, which seemed to turn Derek on further.

After only five minutes of this Casey and Derek broke away from the kiss simultaneously and looked into each others eyes once again. Want was etched across both their pupils and as though they had spoken through telepathy, Casey and Derek took hold of each others hand and headed up the stairs.

Derek found the nearest empty bedroom and led Casey into it before shutting the door.

The room was lit with only the moonlight that shone through the window. Derek recognised it as Ralph's parent's room. It had a large double bed in the centre of the room which was draped with a light blue satin bedcover.

Derek looked over and saw Casey standing in front of the bed and smiling at him confidently. He would never had guessed she could be so confident about something like this, but he couldn't shake the feeling that she looked so incredibly at ease with what was apparently going to happen.

He walked over to her, smiling in response to hers. She took his face gently in her hands and began to kiss him again. This time they kissed more gently, but with unmistakable passion.

Without breaking their kiss, Casey slowly moved backwards, pulling Derek with her, until the back of her legs hit the bed and they tumbled backwards on top of it. They laughed softly for a while before continuing their kiss.

Derek stroked his tongue across Casey's lips until she granted him entry of her mouth. As they explored each others mouths Casey began trailing her hands under Derek's shirt to feel his muscled chest that had been hardened from years of hockey. Derek made a sound that varied between a moan and a growl as her small fingers traced all the lines on his chest.

With Casey's hands encouraging him, Derek stroked Casey's leg from her ankle all the way to her thigh, shifting her dress up further as he reached the top.

Casey, getting frustrated with the obstacle, began trying to pull Derek's shirt off. Derek had to stop what he was doing momentarily to help her.

When they had succeeded in removing Derek's shirt, not wanting to be interrupted from their kiss again, Derek began peeling off Casey's dress. Before continuing their kiss again, Derek took the time to appreciate Casey's slender body. She had a flat stomach that was paired with curvy hips. Her skin was a golden colour that shone in the moonlight. Derek now had a chance to really look at the silky black thong she was wearing that he noticed earlier. It was paired with a thin, black, front-clasp bra that covered her shapely breasts.

He noticed she was watching him take her in and her face was beginning to flush self-consciously. Derek then dropped his head and kissed her neck lightly. He then began trailing kisses down her neck, one onto each breast, then onto her stomach, dipping his tongue into her bellybutton swiftly before continuing with his trail. This move made her body thrust up into Derek's touch. Casey hadn't meant to do this and so she felt slightly embarrassed by it, but Derek didn't seem to think anything of it and so she let it go.

Derek's kisses reached the top of Casey thong and instead of continuing his trail down, he continued in the opposite direction, starting with her legs. He kissed his way up to her thighs and then began kissing the insides of them. Every now and then his tongue would come out and stroke her skin. Whenever he did this, Casey's body would react with a jump or a shiver, which spurred Derek on further.

When Derek reached Casey's panties once more, this time he did not stop. Instead, he kissed along the top of them while his fingers hooked into the leg holes and he pulled them down her legs.

Casey kept her legs firmly together. Its not that she didn't want Derek, it was just that she didn't feel as confident as she did earlier; she figured it was the alcohol losing its buzz. Derek saw how she kept her legs closed and figured she wasn't ready for him yet. He moved his body over her and began working her breasts as his head once again found her lips. He quickly moved his hands to undo the clasp at the front of Casey's bra. As soon as it was undone, Casey's breasts fell from the bra, leaving her completely exposed. He took both boobs in his hands and his thumbs began circling her nipples until they felt rock hard.

Derek broke away from the kiss and Casey stared at him questioningly. He then lowered his head and took her left nipple into his mouth. Casey moaned noisily as Derek suck her nub and fondled her right breast. As Derek worked, Casey would buck her hips underneath his body and he could feel himself getting harder by the minute. Casey could feel his hardness through his pants and so moved her hand between both their bodies and began rubbing him through his jeans. After a while Derek had to stop Casey and get up. His jeans had become increasingly tight and he couldn't take the pain any longer. With an apologetic look towards Casey, he began striping of his jeans till he was left in nothing but red checked boxers. Casey couldn't help but smile at the obvious bulge that she had caused, showing through Derek's underwear. Derek quickly got back onto the bed, but this time he remained at the bottom of Casey. Derek cautiously separated Casey's legs, and this time Casey didn't shy away.

Casey could feel Derek's warm breath between her legs. It sent a tingle all the way through her body that made her toes curl in pleasure.

Derek used his middle finger to swiftly stroke Casey's clit. Casey's hips practically bounced right of the bed from the pleasure that had soared through her. She was desperate to feel more and so opened her legs wider as an invitation for Derek to continue.

Derek noticed a glistening between Casey's legs and he knew that she was wet. He had an unbelievable urge to taste Casey. So he leaned forward and licked his tongue down her folds. He could hear Casey's breathe get quicker and he knew she was enjoying herself. Derek continued to lick Casey's clit, every now and now he would dip his tongue inside her and she would moan and groan louder.

Derek paired his tongue up with his finger, pushing into Casey's folds as he pumped it in and out. By this point Casey was biting a near by pillow to stop her self from screaming out in ecstasy. Derek quickened his pace to match Casey's hip thrusts that were becoming more frequent which told him she was close.

Casey hadn't lied to Derek before, she really had done this with Truman, but it felt nothing like the pleasure she was experiencing now. Casey thought it was strange that the thought of Truman while she was with Derek did not make her feel guilty in the slightest.

Casey's breath got even faster when Derek began sucking on her clit, just like he had done with her nipple.

"Oh god!" she panted as Derek continued to thrust his finger faster into her. "Derek! I'm Cumming!" she screamed as she and Derek felt her body convulse into shivers as she began her climax.

Derek tasted her juices as they flowed out of her, before lifting up to face Casey.

As Casey's tremors finished she saw the shine around Derek's mouth and she shameful went to wipe it from his mouth. Derek caught her hand before she could carry out the task and began licking his lips to clean off her juices.

Casey thought this act was incredibly sexy and she couldn't resist crashing her lips against his once again. They kissed for a few minutes and then Casey felt the hardened bulge in Derek's pants being pressed into her. At this, Casey reached down and began her attempt at shifting of Derek's boxers without interrupting their blissful kiss. Casey had enjoyed the pleasure-filled event that had just taken place, but now she wanted to feel him inside of her more than anything.

Derek noticed Casey's attempts at removing his boxers and so helped her pull them down and then he kicked them off.

Derek's penis positioned itself almost naturally at the entrance of Casey's vagina, as though they were two magnets whose soul purpose was to be joined. The shaft of his penis was teasing Casey's clit lightly. Derek looked at Casey for reassurance that this was definitely what she wanted. She looked back at him and both their gazes were so intense, they almost forgot what they were about to do.

In one swift movement, Derek pushed his cock into Casey's wet pussy and heard her yell out in a mixture of pure pain and pleasure. He remained still for a moment, waiting for her to adjust to his size and ease the pain. She nodded slightly for him to continue now that the pain had subsided somewhat.

Derek stayed at a steady pace for a while, waiting until all the pain had gone and she was moaning in pleasure.

Derek could hear a few grunts and groans that were obviously not coming from Casey and he realized they were coming from him. He picked up his pace, thrusting quicker and harder into her as she egged him on by wrapping her smooth dancers' legs around his butt, using them to push him in deeper.

Loud pants and moans could be heard filling the room as Casey moaned for Derek to go "Faster!"

Derek promptly moved both Casey's legs and placed them next to his head, resting them on his shoulders; this gave him access to go even deeper inside of her, and when she moaned the loudest moan she had all night, he knew he had hit her G-spot.

Derek could feel himself on the edge of his orgasm, but he didn't want to come until she was satisfied. He began banging into Casey so hard that the bed was shifting and smacking into the wall it was resting against. Derek could tell by the response he was getting that she wasn't complaining about his forcefulness.

Casey was close now but Derek wasn't going to be able to hold on much longer. He placed the finger he had been using earlier, in between their bodies and quickly found Casey's clit once again. He then began rubbing it as he continued his hard thrusts into her sweaty body.

This was too much for Casey and she quickly fell over the edge and into her climax as she screamed out Derek's name in pleasure.

"Derek!"

This was Derek's undoing and he swiftly spilled his seed into Casey, before collapsing on top of her. He shifted his body so that he wasn't crushing her with his weight and they both continued to lye there, panting.

After a moment Derek regretfully pulled out of Casey, who moaned in disappointment.

Derek fell to the side of Casey and lay facing her as she turned her body to face him.

"Well I guess Nora was right," said Derek still trying to control his breathing. Casey stared over at him, completely confused as to what he was talking about.

Derek looked at her before explaining. "Leaving school did bring us closer together."

Casey burst out in exhausted laughter, followed by Derek, as she leaned into his naked, sweaty body and lay her head on his chest.

"Thank you," said Casey, without elaborating on what she meant.

Derek knew immediately that she was thanking him for more then just the amazing pleasure he had given her tonight. He wrapped his arms around her moist body and kissed the top of her head. They both knew that at this moment both their lives may have changed forever, but right now, neither of them cared.

Just then the door to the bedroom came swinging open, to reveal a questioning Truman.

"Hey, I heard a noise coming from he-" Truman was cut off through his sentence when he spotted who was in the room and the position they were in. Casey and Derek stared back at Truman, both thinking the same thing;

"Oh crap!"

hope you enjoyed it! and please please review! lo0ves ya all xxxxxxxx