That is Derek's current state of being. His eyes locked on her long wet hair clinging to her soft looking skin, her face turned up towards the water, one hand braced on the tile wall in front of her, the other hand moving in a slow rhythm between her—

Oh. GOD. Is she-? She is. She's touching herself. And suddenly three years of sexual tension, repression, of fighting and arguing with his step-sister, and a year fantasizing about what almost happened that night have all come rushing to a climax, depriving him of his self-control, voiding him of conscious thought, and making him unable to look or move away.

Casey bites her lip, lets out a little moan and her fingers move faster.

He can't take this. What the fuck is she doing taking a shower at one in the morning for anyways? And why is the shower curtain not all the way closed? He suddenly feels like a fucking pervert as he stands there watching his step-sister—HIS GODDAMN STEPSISTER WHO HE CANNOT UNDER ANY CIRCUMSTANCES PUSH UP AGAINST THE SHOWER TILES AND—

No. This is so fucked up. And wrong. And—

Derek groans and Casey's head snaps up. Her blue eyes widen at the sight of him. And when her eyes flicker down and widen more, he knows she is focusing on the very obvious bulge straining against the thin fabric of his boxers.

Her eyes snap back up to his and there is a very long, very awkward silence as they both stand there unmoving, not even blinking.

And it's too much. Casey hates Derek. But she can't help that for the last several months—and just moments ago in the shower—she's been actively fantasizing about her step-brother.

Ever since that night last summer.

It was late, they had been watching a movie with the family, but everyone else had already gone to bed, leaving the two of them, alone and smashed together on the couch. Without thinking—or planning, or over-analyzing, or any other very Casey-like thing—she laid her head on his shoulder.

And a new and good feeling suddenly tingled all over her body when she caught a whiff of his scent—what is that anyways? Is it cologne or aftershave mixed with what? Boy sweat? Why is that so attractive? Goddammit, why is he so sexy? — and felt his body heat so close to hers. Lust and desire. That was the new feeling. And it was overwhelming. And confusing since this was Derek. And she hated him.

When she chanced a glance up, she gasped. Their eyes had locked and she realized he'd been staring at her. His dark eyes flickered once to her lips. He leaned forward, almost imperceptibly. Casey let out a shriek and bolted upstairs.

They spent the next several days avoiding each other. She went back to Queens early, giving her mother some lame excuse about studying even though the semester was starting for two more weeks.

This time he's the one who runs away. Casey stands there shivering for several long minutes. Her friend from college, Samantha, had told her "Just do him and get it over with already!"

And right now, that's all she can think about. It's not like she has feelings for him. And it's not like anyone would find out or have to know.

That's all it takes. Her normal self has lost control. She turns off the water, towel dries her hair. She wraps the towel around her body and walks straight into Derek's bedroom.

She finds him, with his back to her, hovering over his dresser, and knuckles white against the edge. Without a word or a sound, she pads her way across the room, drops the towel and presses herself against his back. She wraps both arms around his waist.

"Casey, what the—" he stammers. Her hand smooths over his hard abs and beneath the waist band of his boxers. She's nervous. God, please don't let him notice my shaking hand.

He tries to protest, but just groans when her hand wraps around him and strokes him ever so lightly. "Casey, we...I can't...oh god...we—"

"Shhh," she coos, standing on her toes and kissing his neck. She's really not sure where this sudden confidence is coming from, but it has to be at least partly from the intense desire thrumming in her veins.

Casey grabs his hand and places it between her legs. He groans as his fingers sink into her soft wet warmth. A second later, he spins her around and sits her atop his dresser, a question in his eyes. He doesn't remove his hand though. Instead his fingers plunge deeper into her.

"Derek," she moans. "Derek, I hate you."

He smirks. It's the first Derek-like reaction since he caught her in the shower. It sends a thrill through her. He lifts an eyebrow for her to continue.

"But I need you to—"

She stops, tilts her head back, and bucks her hips against his hand.

"Need me to what, Princess?"

He presses his thumb against her firmly, and curls his fingers, pumping harder and faster. Before she can answer, her whole world explodes. It's the most out of control he's ever seen her. And it's so fucking sexy he just wants to—

He removes his fingers, grabs her face and crashes his lips to hers. Derek carries her to the bed and in under a minute he's inside her. He moves slowly at first, then faster and harder as she cries for more.

And all he can think is finally. He collapses on top of her breathless, feeling drunk or high. But better.

"I still hate you," she murmurs against his neck. He chuckles.

After a minute, Derek rolls over, pats her on the butt, with a wide shit-eating grin on his face, "Go to bed, Princess."

She scowls, he winks. Casey huffs and marches off to her room.