Peanut Butter

"C'mon, D, it's been like a month," Casey whines, but her tone is playful, as she crawls onto his bed and lies down beside her step-brother.

Derek laughs, turning on his side, placing a hand on Casey's thigh and dragging her leg up to rest on his hip.

Casey traces her fingertip along Derek's jaw, her mind going fuzzy at the scent of his cologne.

"The longest we've ever gone was five days. It's been almost five weeks," Casey whispers, scooting closer, pressing her body against his. "I'm losing it."

Derek smiles, wrapping his arm tightly around her waist.

"Yes, and if I recall correctly, that five days was when we were home for Spring Break," Derek drawls, leaning in closer. "And you and I both know how that ended."

Casey bites her lip, surging forward, shoving Derek onto his back. She sits upright, straddling his hips.

"I do, but nobody will be home for hours this time," Casey points out, leaning down to press her lips to the side of his neck.

Derek exhales heavily, his hips bucking up against Casey involuntarily as his fingers dig into her hips.

"Case," Derek warns, tipping his head back against his pillow.

Casey sits back, smirking down at her step-brother as she tears her t-shirt up over her head and tosses it aside.

She watches as Derek's pupils dilate and his expression turns dark when she unhooks her bra and slips it off.

Derek digs his fingers deeper into her hips.

Casey slides off of Derek's lap, standing at the side of his bed, smirk still plastered on her face. She locks her eyes with his, her fingers moving to the button on her jeans.

She pops the button and undoes the zipper, dragging her jeans down her legs and kicking them to the side.

"Caaasey," Derek groans, his fingers twitching at his sides. "Your mom is actually going to kill me this time if she finds out."

Casey hooks her thumbs into the waistband of her underwear, sliding them down and off before rejoining Derek in his bed.

"Well, the sooner you get over here, the sooner we'll be done and nobody will suspect a thing," Casey laughs, crawling under the comforter.

Derek smirks back at her, stripping off his t-shirt and joining his step-sister under the blanket.

"Uh-uh," Derek whispers, his voice low and gravelly as he leans in and captures Casey's lips in a kiss. "We haven't had sex in a month, we won't be done any time soon."

"Wow," Casey breathes, her chest heaving.

Derek nods in agreement, his hand gliding over her side.

"Yeah," Derek agrees, pulling her close against him with an arm wrapped around her waist. "That was…"

"Incredible," Casey finishes, tangling her fingers into his hair.

Derek leans forward, pressing his lips to hers.

"I love you," he whispers, smiling against her lips.

Casey smiles back, pressing her body as close against his as she can get.

"I love you."

Derek's smile widens as he leans his forehead against hers.

"It only took us ten months to get here," Derek laughs lightly, turning to look over his shoulder to check the time, making sure there won't be any interruptions any time soon.

Casey shakes her head, drawing patterns on Derek's bare bicep with her finger.

"I really did think that's what you wanted," Casey whispers, a little embarrassed.

Derek kisses her forehead, brushing a strand of hair out of her face.

"I want you," Derek clarifies, running his thumb along her cheekbone.

Casey bites her lip, tangling her legs with his under the comforter.

"I want you too," Casey tells him, pressing her lips to his. "It'll be complicated and messy, but I love you. Mom and George know already, so it'll just be the rest of the family we have to explain it to."

Derek purses his lips, exhaling.

"Lizzie knows too," he says, watching as Casey's eyes widen.

Derek laughs lightly, remembering the night Lizzie interrogated him when he and Casey first got back from school for the summer.

"Well, then," Casey laughs in response, shaking her head. "I love you, Derek Venturi. I love you so much. I don't know what that's going to mean for the future, but it's the one thing I know for sure."

Derek smiles a huge smile.

"What it means, Princess, is that one day, Casey McDonald will be Casey Venturi," Derek says, his voice confident. "I'm gonna marry you one day. I know you'll make me wait until we graduate. But rest assured, you're getting a ring and the huge, fancy wedding you've always dreamed of. And it'll be me waiting for you at the end of the aisle, not some other loser."

"So, did I hear you correctly before?" Casey laughs, sucking peanut butter off of a spoon in the kitchen after she and Derek got dressed and out of bed.

Casey is leaning on her elbows on the kitchen island, with Derek sitting in one of the stools across from her.

"That depends," he laughs, smiling a half-smile at her. "What are you referring to?"

Casey smiles around the spoon, walking around the island to stand in front of him.

Derek's arms immediately snake around her waist, pulling her toward him.

"Well, I'm pretty sure you proposed," she says, laying her forearms over Derek's shoulders after placing the now-clean peanut butter spoon on the counter. "Or was that just the sex talking?"

Derek laughs again, looking up at his step-sister, smiling.

"Well, you being naked in my bed could probably get me to agree to just about anything," he jokes. "But no, I did not propose— I merely said I plan to."

Casey shakes her head, laughing in return.

"I think that's a distinction without a difference."

Derek smiles again, standing from his chair and pulling her tight against him.

"Oh, no," he explains. "You'll know it when I ask you to marry me."

Casey bites her lip, fiddling with the hair on the back of Derek's neck.

"Lookin' forward to it."

Hello, friends. Sorry it's been longer than I usually go between uploads. It's been a hell of a week. This one-shot is part of my most recent series. The chronological order is, "Alabama", "S.O.S.", "Party", "Red-Handed", "Comfort", "Talk", and "Peanut Butter". There are three more in this series.

Thanks for reading.