Disclaimer: I don't own "Life With Derek" or any of its characters. I'm just borrowing them for my own amusement...and hopefully yours too.

A/N: Sorry if characters are a little OOC. I tried my best. Hopefully more one-shots will follow this one and then I can work my way back up to writing chapter stories. I just don't have the discipline (or the skill, in my opinion) to do a full-length story. Please review! Constructive criticism is always encouraged and flat out praise is well-received too.

Casey appraised her reflection with critical eyes. The red silk dress that she was wearing was breathtaking. Her makeup was perfect. Brown curls delicately cascaded over her otherwise bare shoulders. All the outfit needed was a personal touch: the golden heart pendant that Derek had given to her for her birthday. Just as she was about to put it on, footsteps alerted her to someone entering her room. Briefly catching a glimpse of his reflection in the floor-length mirror, Casey smiled, but she did not turn around. Instead, she sprayed on perfume as she heard the door click as her visitor closed it behind him.

"Hot date?" Derek teased, crossing the room to stand behind her. Casey observed his expressions in the mirror. Though his voice had a teasing lilt to it, she detected darker undertones and his whole body looked tense--despite the fact that he was obviously trying to hide it. Casey held up the locket and Derek took it from her, complying with her silent request. The brunette held up her hair and Derek pulled the necklace around her neck, skillful fingers opening and closing the clasp before he pressed a kiss above it.

"Maybe," she replied, trying to ignore the pleasant tingling on the back of her neck.

"Where is he taking you?" He asked, eyes roaming over her body appreciatively. The corner of his lip twitched as he thought about other hands sliding over those hips that he'd so carefully mapped over the last three and a half months.

"I don't know yet. We might just hang out at his place," Casey answered vaguely, grabbing her lip-gloss off of her desk. "That's where we always end up anyway," she giggled, discreetly gauging his reaction as she swept the wand across her lips. Brown eyes bulged and narrowed as Derek took a deep breath--fighting off shadowy images of lips meeting and sweaty limbs tangling under cool sheets. Had it been Derek with Casey, these mental pictures would have been more than welcome, but they were of her and a faceless mystery man instead--whom he had already decided he hated.

"So, who's playing Romeo tonight?" Derek asked through gritted teeth, trying desperately to play it cool and failing miserably. Casey smirked at him in the glass and then turned around so that Derek could see the impish glint in her eye as she took her sweet time.

"You." Casey wound her arms around his neck and toyed with the hair on the nape of his neck--sending shivers down his spine. The change in Derek's attitude was instantaneous. First, every muscle in his body relaxed as his imaginary rival disappeared. Then his hands looped loosely around Casey's hips, almost in a possessive manner, and he smirked, bringing her in closer. But as a realization hit him, his face fell and he pushed her away.

"Wait, what was that all about then?" Derek demanded hotly. "You may think it's funny to toy with me, but it's not quite so amusing from over here." Casey's mood shifted as her lips curled into a sneer.

"Thought I'd give you a taste of your own medicine for once," she snapped bitterly. Derek's face contorted with confusion.

"What?"

"Oh, don't play dumb. I'm not one of those brainless floozies that you parade around school." Casey crossed her arms and cocked her hip to one side, "Oh, and speaking of your bimbos…" she trailed off, raising an eyebrow pointedly, knowing that he'd put two and two together. Derek's throat tightened. So tonight was the night. He knew it would come. She knew it would come. The only question had been when. Derek wondered for the hundredth time why he hadn't prepared for it, cursing himself over and over.

"Casey," Derek started. She waited for him to continue, still furious with him. "What do you want me to say?" he pleaded. Casey let out a bitter laugh.

"Well, you could try starting with an apology," Casey suggested sharply. Derek visibly winced, drawing back slightly as if he'd been burned.

"For what? We're not exclusive. Technically, I haven't done anything wrong and you know that," he replied defensively. This was a very bad move on his part.

"Technically," she repeated quietly. "Technically?" Derek swallowed the growing lump in his throat, back-pedaling fiercely.

"No, I--"

"Shut up, Derek!" Casey snapped. Derek's mouth closed and Casey stepped forward. "Our whole relationship is about the technicalities, isn't it? It's all about the small print, the fine lines. Technically you haven't done wrong by me because technically we're not exclusive. Technically I'm allowed to date other guys, though you'd blow a gasket if I did. Technically you can date other girls, but it kills me and you know that." Derek opened his mouth to protest, but Casey jabbed him hard in the chest, going on. "Technically we're not related, so it's okay for us to want each other, but no one else can know that because technically we're family," she ranted scornfully, careful not to let her voice carry outside of her room.

Derek was stunned speechless. He'd known all of it, that much was true. He just never put a whole lot of thought into it. It wasn't like he went out with other girls to hurt Casey. He just considered himself a realist and the facts were that they could never really be a couple. It wouldn't just be social suicide, but their family would probably disown them. The truth of the matter was, Derek never considered their relationship anything but a fleeting fantasy that was bound to fade once reality set back in--no matter how much he wished it could be more.

"Well?" Casey looked at him expectantly. After a few minutes of silence, Casey snorted. "Of course. You're probably standing there trying to calculate which is closer: the door or the window."

"That's not fair," Derek protested, hoping she wouldn't notice that he wasn't denying her claims.

"No! You know what isn't fair?" Casey's bottom lip trembled as tears filled her eyes. "Kisses in dark hallways, presents to make up for broken promises, indifference or insults whenever other people are around." She rubbed at her eyes angrily. "Greeting you and trying to pretend that you don't smell like some other girl's perfume." She swallowed thickly and mustered up all the strength she could manage. "Well, I'm done."

Never had Derek imagined that it would hurt that much. As he stared into those piercing blue eyes--and reality sunk in--his chest caved in. Or, at least, that was what it felt like. He wanted to beg, argue, plead for her to change her mind, but he couldn't breathe, let alone speak.

Casey turned away from him and grabbed a tissue to dry her eyes with.

"You don't mean it," Derek said shakily, grasping at straws. Steeling herself, Casey whirled around with determination hardening her features.

"No, Derek, I do. I've had enough."

"But--" Derek grabbed her shoulders, running his hands down her arms. She tried to shrug him off, but he laced his fingers with hers. "Please, give me another chance." The desperation in his voice kept her from trying to push him away again.

"Another chance to what, Derek?" she asked softly. "To date other girls? To make fun of me in front of your friends and then pull me into a closet to make out fifteen minutes later?"

"No…"

"Derek, I want it all. I want commitment, I want real dates, and most of all I want to hold your hand as we walk down the hallway in school," she explained, hope shining in her eyes. But the panic that was written all over his face gave Casey her answer. It would never happen. So she pulled away from him.

"What if I promise to be nicer?" Derek offered hurriedly. Casey's curls shook back and forth as the tears finally fell from her eyes.

"It's not enough." Acting quickly, she crossed her room to the door and opened it, but Derek caught up in a flash. He ran after her and promptly closed it, leaning against it to hold it shut.

"Casey, I can't lose you," he begged, grabbing for her hands again, trying somehow to appease her without giving her what she really wanted.

"No, Derek. You can't keep me." Giving him one last kiss, Casey opened the door and pushed him out before he could register what was happening. Then she closed the door and turned the lock, laughing bitterly at the irony. After all, it had really been him who had shut the door on her.