AN: Well usually I hate songfics, but this kind of crept up on me, you know? It wouldn't leave my mind, so it had to be written.

Disclaimer: Life With Derek is not mine, the songs aren't mine, everything that's less creative is mine, though.

Summary: Based off of A Rocket To The Moon's song Like We Used To. Away at college, Derek and Casey share an apartment. They were together for some time, but eventually decided to break up because of their family. Basically, this is Derek remembering what they had and hoping Casey's happy. Very angsty.

FULL VERSION WITH HAPPY ENDING IS POSTED AS WELL. I just kind of like this alone, too. It was never intended to go past this one shot form, but people are babies and don't like angst.

Italics is Derek remembering back to them being together, plain text is recent.

Warm breath ghosted across Derek's neck and he smiled sleepily. God, he loved this. He opened his eyes and watched the blurry brown blob turn into beautiful brown locks of hair. He buried his nose in Casey's hair and breathed deeply, an intoxicating smell of strawberries assaulted his nose and his smile grew. He sighed happily, "mmmm." Normally, Derek wasn't one to cuddle. But normally, one wouldn't wake up next to their step-sister after a long night of playful conversation and giggling.

Casey snuggled closer into his chest and wrapped her legs around his own. Derek squeaked, a very manly squeak!, as her cold toes slide across the back of his knee. "Casey, always so cold, Baby." he breathed out before wrapping his arms more firmly around her. A giggle escaped the girls lips as she shifted under the covers to his chest, pressing her ear firmly against it. This was something Casey loved to do, and he knew it. Listening to his heart always made Casey feel good. Sometimes, she'd listen after a long day of classes and studying to ease her frustration. Sometimes she'd listen to lull herself to sleep. Sometimes she'd just listen.

Derek hummed happily and sang Casey's favorite song quietly to her, willing this feeling to never leave.

I can feel her breath as she's sleepin' next to me,
Sharing pillows and cold feet.
She can feel my heart, fell asleep to it's beat,
Under blankets and warm sheets.

A groan escaped his lips as Derek sat up in bed, dangling his legs off the side. He sighed and brought his hand to the back of his head, musing the back of his hair and scratching his scalp absentmindedly. He tried to forget, he willed himself to forget everything. He looked back at the pillow on his bed, the one that hadn't been occupied the night before, and felt a familiar stinging in his eyes. No, he refused to cry.

Derek let out a loud, angry grunt and got up, shuffling to the closet. He picked out some clothes and made way to the bathroom. he braced himself at his bedroom door, delaying the inevitable. He knew he'd see Casey, of course he'd see Casey, why wouldn't he? They shared an apartment, dammit.

Who's bright idea was that? Derek grumbled. Of course, it wasn't a problem a couple of months ago, when they were... together. No, it was quite amazing, actually. Ever since they decided it was best if they stayed just friends, "best friends Derek, best friends," though, it was torture. Actually, it wasn't torture at first, he wouldn't lie to himself. At first, there was possibility. Possibility that maybe, just maybe, Casey would change her mind and put her happiness above their family's. That possibility vanished a few months later when she started dating Sam again. He told her he was happy for her, and he was, but he wasn't happy, himself.

The stinging in his eyes was back, and all Derek could do to distract himself was bite the inside of his cheek as hard as he could, the, now familiar, rusty taste flooding his mouth. He braced himself as he opened the door, making his way to the bathroom. The least he could do was feel a little more awake and refreshed before he had to face Casey.

He made his way down the hallway and reached for the handle of the bathroom door, but quickly glanced at Casey's door first. He shouldn't have. The stinging in his eyes was back and he knew that Sam was in there with her. A silent sob racked his body and he ran into the bathroom slamming the door behind him. He couldn't have another break down, he wouldn't.

"Dammit Casey, why?" he whispered to himself, like he did every morning for the last year and half, why couldn't they just be happy together and fucking forget everyone else.

If only I could be in that bed again...
If only it were me instead of him...

Derek laughed quietly as Casey jumped up and down happily.

"Thank you, thank you, thank you, Derek! I love you!" He watched her run around their apartment getting ready for the movie. She shuffled around the kitchen making popcorn and grabbing anything else she could think of, then moved to the hall closet, grabbing as many blankets and pillows as her arms could shook his head and laughed before getting up to help her. He stood behind her and whispered in her ear humourously, "don't cover you line of vision, Baby, we don't need any klutzilla moments ruining the night."

"Der-ek!" she whined, trying to hold back her smile. He did notice she dutifully lowered her arms so she could see in front of her, though.

Casey loved when they had movie nights. They would gather all the blankets and pillows they had and make an extravagant bed in the middle of the living room floor. Derek would grab all Casey's favorite movies, Derek made movie nights all about Casey, and pile them by the DVD player, and she'd chose which order they watched them in. All the junk food in the house was strewn across the floor around them, and there was a silent understanding that everything else in the world was forgotten. This was Casey and Derek time.

Movie nights usually took place on Friday nights, they'd stay up all night, sometimes well into the next day, watching movies, or not, and just enjoying each others company. One time, they stayed together in their own little bubble for so long that it was pushing noon on Saturday before they realized they had lives they needed to tend to.

When they finished setting up the living room, Derek threw himself down, laying on his stomach. Casey laughed above him, "you're so graceful." He turned to look over his shoulder and winked. "You know it, Princes."

Casey sat next to him before glancing at the movie selection, grabbing one near the bottom of the pile, and tossing it by Derek's face. "That one," she smiled and made to lay down next to him. As he set up the movie, Derek watched her in his peripheral vision. Casey scooted her way towards the candy and bit her lip in concentration. Derek knew she always picked the the same thing first, but she always made this huge show about not being able to decide what she wanted. Derek pressed play and situated himself next to Casey, "twizzlers," he whispered in her ear just as she reached her hand out to grab something. "How'd you know?" she gasped, truly surprised, brows furrowing in confusion. "You're predictable, Space," he laughed, "the movies starting." Casey wiggled her way closer to Derek, twizzlers in hand, so that their bodies were touching, shoulder to ankle.

"Oooh! I love this song!" she smiled as the opening credits started, and Derek turned to face her, breath ghosting over her ear. "I never meant to cause you any sorrow, I never meant to cause you any pain, I only wanted one time to see you laughing, I only wanted to see you laughing in the purple rain." Derek knew it was one of her favorite songs, she fell in love with it while practicing for her last dance performance.

Casey smiled and turned to kiss him. Her lips ghosted over his before he tilted his head to firmly kiss her back. He broke the kiss to roll onto his back and looked up at her expectantly, a smirk on his face. Casey rolled her eyes but leaned down to kiss him again.

Derek's heart was beating erratically in his chest as Casey leaned above him, kissing him deeply. If everything else in his life fell apart, he'd be happy to just be here, with Casey.

Does he watch your favorite movies?
Does he hold you when you cry?
Does he let you tell him all your favorite parts when you've seen it a million times?
Does he sing to all your music while you dance to "Purple Rain? "
Does he do all these things, like I used to?

"Derek!" Casey slammed the door to their apartment, typical Casey-Freakout-Mode. "Derek! Where are you?" she screamed, uncharacteristically throwing all her stuff down at the door and looking around frantically. Derek came out of the kitchen, two sodas in hand, and sighed. "What happened Case?"

Tears welled up in her eyes as she looked at Derek, "Iditmenferitohapnijdtdiissry!" her arms wrapped tightly around his neck and she clung to him for dear like.

Derek felt sick, a tight coil wrapped up in his stomach and saliva pooled up under his tongue. He knew she was with Sam before her dramatic entrance, he just didn't know what exactly happened.

It clicked. Derek bit the inside of his lip, blood stinging his taste buds. Oh, God, please no... "Spacey, tell me what happened." he begged, trying to remain calm for her sake.

She looked up from his chest, tears pouring down her face, and caught his eyes with her own. Sorrow darkened the blue orbs and she tried to catch her breath. "Derek," she cried, "I can't believe myself, I wanted to wait, I was caught up in the moment. It wasn't even nice! We were in his car Derek! His freaking car. I should have stopped him, I wasn't thinking. " Everything ruched out of her mouth, a steady flow of words digging into his heart and scooping out pieces to throw away. She choked out more, but the rest was unintelligible as she cried in his shirt.

Derek bit harder down on the inside of his cheek, welcoming the pain and pushing back the tears. He could barely think straight. No, no, no, no, no, no, no, no!

Casey slept with Sam. In his car, none the less. Anger bubbled up in his chest and he fought to keep it in check. Who does Sam think he is? Anyone who knew Casey knew she wanted to wait.

Derek remembered back 14 months ago when he could've been with Casey. They never went all the way because he knew, Derek knew, that Casey wanted to wait and she'd never forgive herself if they went all the way. He remembered the way her fingers trickled across the skin below his belly button, wanted to go further, but what to stop at the same time. His lips wrapped around her ear lobe, gently sucking, as he chuckled lightly in her ear, thinking he'd have forever to be with her. "Mmmm, not yet Princess." he'd whispered, sending shivers through her body. At the moment, Casey was upset, but whenever she though back to that moment she silently thanked him for doing what she couldn't.

Derek couldn't stop the stinging behind his eyelids this time, he couldn't hold back the tears that flowed, and he couldn't stop Casey for looking up at him and seeing. Derek didn't do emotions, Casey saw that he did.

Her own watery orbs met his, saying things she'd never be able too. I'm sorry, Derek. I still love you, Derek. I wish it had been you, Derek.

They held each other all not, not speaking, just crying. Casey cried for something she'd lost and couldn't get back. Derek crying for what should have been his, but wasn't. Dammit Casey, why?

Fourteen months and seven days ago...
Oh, I know you know,
How we felt about that night.
Just your skin against the window...
Oh, we took it slow,
And we both know...
It should've been me inside that car.
It should've been me instead of him... in the dark.

Derek laughed when Casey flung a green bean across the table at him. "Oh no you don't!" he cried dramatically, pushing his chair back, ready to stand up. Casey saw what he was going to do, squealed, and unceremoniously threw herself from the kitchen table and flew down the hall, giggling the whole way.

Derek leaped after her, snatching her at the hips, and tickling her furiously. "Der-ek!" she choked out, laughing and gasping for breath. Derek was laughing just as hard, staring down at the beautiful face before him that was lit up in pure happiness. "Der!... Can't... Breath!" she laughed and laughed, willing him to stop, but keep going at the same time.

Casey sighed in relief as he took mercy on her and finally stopped his ministrations. They were laying on the floor in the hallway, him slightly on top of her, breathing deeply with huge smiles on their faces.

He lifted his head to look down at Casey. Her hair was sprawled out around her in a complete mess, he cheeks were bright read, and her eyes still held a twinkle of laughter in them. She was the most beautiful thing he'd ever seen. "God, I love you!"

Casey smiled up at him, feeling happier than she ever had, and whispered back. "I love you too." Derek couldn't help himself, he leaned in and kissed her.

"So perfect," he whispered against her lips, smiling and completely carefree. He pulled back and hugged Casey to him, rolling over onto his back. Her head found its usual position on his chest, right above his heart, and she listened carefully. She listened as the beat slowly evened out as Derek played with her hair quietly.

These were the moments the two cherished the most. When they could just be together, quietly, no one but each other. Derek holding Casey closely, loving how good they felt together. Usually it wasn't on the floor in the hallway, but that didn't matter. Nothing mattered when they were together like this. Only each other. Only Derek and Casey and their love for each other all wrapped together feeling more happy than either of them could have thought possible.

Will he love you like I loved you?
Will he tell you everyday?
Will he make you feel like you're invincible with every word he'll say?
Can you promise me if this was right:
Don't throw it all away?
Can you do all these things?
Will you do all these things...
Like we used to?
Oh, like we used to...

Derek watched his reflection in the mirror, hating himself for being so weak. Glassy brown eyes stared back at him, tears streaming down the cheeks of the man who refused to show emotion. He choked back sobs, trying to be quiet, Casey was out there, Sam was out there, and those three awful words were out there too.

Who would have thought the words uttered out of those soft pink lips that once made him feel so whole and happy would now tear him apart?

It was the first time he heard them. Well, directed at Sam anyway, and he knew it wouldn't be the last. The image of Casey smiling up at Sam whispering, "I love you" burned behind his eyes and more tears rolled out.

God, he was being stupid, It's been over a year since Casey had been his, even if he still wished she was.

Derek breathed deeply, calming himself down and trying to think rationally.

Derek's back leaned against the wall, and his butt slid to the bathroom floor. He sat, head hanging between his knees for what seemed to be eternity, willing himself to stop crying.

At least she's happy. His heart hurt thinking about all the things she now had with Sam, things they'd had together not so long ago. The thought of her smiling and happy brought him at least a little bit of consolation as he wiped his face on the long sleeve of his t shirt. She better not screw this up for herself again, Derek thought bitterly, shocking himself. He was happy for her, of course he was, but he wasn't happy.

Derek wondered if he'd ever be able to actually be happy without Casey.