Author's Note: I was debating on posting this story for awhile but I've finally given in since I haven't posted any LWD fics recently. I have a few ideas for it, but we'll see how it goes ;-) Let me know if you think I should continue it... here's a brief opening so I can get some feedback on whether I should continue or not.


"You. Are. INFURIATING!"

Derek only laughed as he watched his stepsister have a total conniption, punching him on the chest and then shoving past him with a laundry basket full of pink clothes once again. Casey let out a scream of anger and threw his damp red sweatshirt down the stairs so it landed on his head where he stood at the bottom.

"Thanks, sis!" Derek just smiled his amused smirk. He thoroughly enjoyed every single moment of aggravating Casey. She was such an uptight girl, and that's why he had so much fun messing with her. She was too easy to mess with.

He heard a shriek from upstairs and couldn't help but widen his grin. She must have found the little present he had left for her on her desk.

"DEREK!" Casey came bombing down the stairs, holding the offending object in her hand, as far away from her as possible. "What IS this?"

"Lunch?" Derek offered with a shrug. "From… two months ago?"

Casey gagged, throwing the mouldy sandwich onto the floor. "You're so gross!" she exclaimed, wiping her hands furiously on her pink corduroy pants.

Derek pretended to look hurt. "Aww, you don't mean that, Case."

Casey didn't even want to respond to him. She was too angry. She just rolled her eyes, stomping up the stairs again. "And DON'T go into my room again!"

Derek gave himself a triumphant smile. He was getting good at these stepsister pranks. It was his favourite part about having two new stepsisters. Of course, Casey was much more fun to pull pranks on. Lizzie never seemed to get angry. She just gave him the deadly glare that she had. All it did was weird him out.

But Casey… Casey always got so riled up about it. She'd cause a scene. Sometimes she'd throw a tantrum. There were other times she'd even call a family meeting to be able to shoot her mouth off. Derek's favourite times were when she would get physical with him; she'd throw her weak punches and shove him as hard as he could—which wouldn't even budge him.

It always gave Derek a great deal of amusement.

Her blue eyes would darken and her nostrils would flare, and she'd end up stomping her way up the stairs all dramatically until she finally got over it… usually by dinner time.

It was all a game to him. Entertainment. Good fun.

But his fun had been diminishing lately. And it was all because he had told Sam that he was okay with him dating Casey. His best-friend dating his stepsister. What was he THINKING when he gave them his approval?

He had been hoping that things wouldn't change too greatly. But deep down he knew that they would. He didn't get to pick on Casey as much as before… she was always too busy on the phone flirting with Sam. And he didn't get to hang out with Sam as often anymore… he was always making plans with Casey before making any plans with him.

When Derek actually did get allotted some time to hang out with his best-friend, Sam would always find ways to bring up his new girlfriend. How cute he finds it when she laughs. How hot she looked that day.

Derek tried to ignore it at first, but all of the Casey-talk began to affect him. And it wasn't in a "please stop talking about your stupid girlfriend to me 24/7." It was more like a "how dare you talk about my stepsister in that way." He got offended when Sam talked about Casey.

Even jealous…?

What Derek couldn't understand was if he was jealous of Sam's committed relationship (since Derek could barely stay with one girl long enough for a second date) or if it was because it was Casey, his own stepsister, that made Derek feel so… possessive all of the sudden.

He would grit his teeth when Sam would comment about Casey's well-developed curves. He would clench his fists when Sam spoke about what a great kisser Casey apparently seemed to be.

And late at night, Derek wondered if it angered him because he would never be the one to caress those curves or experience a kiss with Casey. Because she was his stepsister.

He could never think about her that way.

Never let his eyes linger on that small patch of silky flesh that peeked out from under her shirt when she stretched at the breakfast table.

Never let himself focus on her full plump lips (that his best-friend had gone on and on about) while she yelled at him.

Never close his eyes to picture her when he relieved his pent up sexual tension in the shower all alone.

He couldn't. He just couldn't.

But he did…