A/N: So this is my second attempt at a one-shot. Thanks to everyone who reviewed my other story, those comments really made my day.

I don't know how well the title works out, but I liked it, so whatever.

Disclaimer: I don't own Life With Derek, but if I did I wouldn't be writing this; I'd be off living my life with Mike Seater.

Sitting on the couch, Casey made no comment about Derek's presence in his prized recliner or the firm grip he had on the remote. According to the schedule that the parents had set it was her appointed TV time, but for once she was not going to fight with Derek for control over the television. She never won these fights; all she ever got was a headache and maybe a bruise for her efforts. So she, Casey Macdonald, was going to do something completely out of character and give up.

Derek was waiting patiently, but eagerly, for Casey to start bitching him out for being in the living room. He knew it was her time with the TV, that's the only reason he was even watching it. He loved picking fights with her; it was so easy to get her going. And anger, well, anger did something to her. It transformed her; it took her from an uptight princess to, well… the opposite of an uptight princess, in a matter of seconds. With her chest heaving, her hair in disarray, and her normally pale blue eyes dark and glittering, she looked amazing. It was during their fights that Derek would catch a glimpse of what an uninhibited, unrestrained Casey would be like. So Derek continued to flip through the channels, looking for a show that would annoy Casey more than wrestling.

When the show came to an end without there ever having been a word from Casey, Derek couldn't explain what he was feeling, but he knew it wasn't good.

They went on like that in the days that followed, with Derek trying to bait her and Casey ignoring his efforts. It was really starting to piss Derek off. She wouldn't even glare at him or roll her eyes; it was like he didn't even exist. Derek wasn't used to being ignored by anyone, especially not by girls, particularly Casey.

Dinner Friday was the straw that broke Derek's back. He had thrown his roll at Casey, hitting her right between the eyes, but she gave no sign that she had even noticed. So when she excused herself from the table and headed up the stairs Derek got up and followed her, heedless of the curious stares he was receiving from his family.

Seconds after she closed her door, Derek busted in her room, slamming the door shut behind him.

Spinning around to see a furious Derek in front of her, Casey asked in confusion, "What the hell is your problem?"

His eyes narrowed. "So you're talking to me now?"

"What?"

"Oh, come on," he scoffed. "Everybody's noticed how you've been giving me the silent treatment this past week. What I want to know is, why?"

It was Casey's turn to scoff in disbelief. "Why do you think? I am so sick of fighting with you all the time. Yeah, sometimes it's entertaining, maybe even fun," she conceded, shrugging her shoulders. "But, other times… it's just too much."

When all he did was cock an eyebrow, she continued.

"I don't like you when you're being hateful," she said frankly. Something akin to hurt flashed briefly in Derek's eyes, but Casey didn't see it. "Even worse, I don't like myself when I respond to your behavior by behaving in the same way. It had to end," she finished, with finality heavily coloring her voice.

Derek felt… funny. It was like the end of an era for him. It had never occurred to Derek that Casey would ever give up fighting him.

"Whatever," he muttered, turning to leave.

Meanwhile, Casey still didn't understand his behavior, sure he was angry—which, considering his reason, was weird enough—but he also seemed like his feelings were hurt.

Placing a restraining hand on his arm, Casey urged him to stay with sheer will. Sighing as if he couldn't believe what he was doing, Derek dropped his hand from the door knob, but he didn't turn to face her.

"Why do you even care that I wouldn't speak to you?" Casey asked bluntly.

When no answer was forthcoming, Casey tugged forcefully on Derek's arm and asked again, this time with a distinct edge to her voice. "Why do you care? You have been a complete ass to me since I moved in. You've made it crystal clear that you don't want me around your house, your school, or your best friend. And, I don't know how many times you've told me to 'shut the hell up.' So, I'll ask you again," she said smartly. "WHY DO YOU CARE?"

Derek turned around and just stared at her. His mouth kept opening and closing like he wanted to say something, but just couldn't bring himself to speak. Right when Casey was going to tell him to either spit it out or leave, he did the impossible…

Leaning in, he grabbed Casey by the shoulders and kissed her. Not a brotherly peck on the cheek either, but a full on kiss on the lips. At first Casey didn't know how to respond. Part of her, the rational, sensible part, wanted to push him away and slap the shit out of him for even daring to kiss her, but as soon as his arms wrapped around her waist and his tongue began running along her lips seeking entrance to her mouth, she closed herself off to sanity and gave in.

She ran her fingers through his hair and pressed as close to him as possible. Casey Macdonald, know grade-grubber, proven klutz, was living out the fantasy of every girl at her high school—and loving every minute of it.

Finally, the need for oxygen overtook them and they broke apart, both were panting heavily, trying to catch their breath.

Casey had no idea what to say. What did one say after having a serious make out session with one's step-brother? Hell, she usually didn't know what to say after a regular make out session, with someone she wasn't related to—but, apparently Derek did.

Catching Casey's eye, Derek said, with his trademark smirk back in place, "That's why." Leaving a stunned Casey behind, he turned and left the room.

Catching sight of her tousled hair and kiss-bruised lips in the mirror, Casey couldn't help but give a small smile.

"I guess he told me."

The End

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