Prompt: the first time she lets him fuck her without a condom.
A/N: This really can be set anytime in seasons 5 or 6, but I wrote it with mid-season 5 in mind, sometime between "Probable Cause" and "Significant Others."
It was late when they returned to Castle's loft. They'd caught a break in the case they were working just as they were wrapping up for then night at 9, a credible tip coming in claiming that their suspect was holed up in an abandoned building in Brooklyn. So they'd went to the address, Ryan and Esposito backing them up, and found their suspect, Mark Holmes. Or, what was left of him, anyway.
Upon first look, it appeared that he'd offed himself via a bullet in his mouth, but Lanie questioned the validity of the theory. It was possible, she said, that someone had staged it to look like a suicide, but she wouldn't know for sure until she did an autopsy in the morning.
By the time they managed to head home to get some sleep, it was nearly 2 in the morning. Surprisingly, Kate was far from tired, still running on the adrenaline of kicking down ten doors before finding the right room. She grinned. There was always one method of tiring her out that she could count on.
"We need sleep," Kate said casually as she followed Castle into the bedroom. She unholstered her gun, double checked that the safety was engaged, and slid it and her badge into the nightstand drawer.
"I'm not tired," Castle replied, hanging up his blazer and slipping off his shoes.
"Me, neither," Kate said. She gave him a sly smile and gripped the hem of her heather gray sweater, quickly pulling it over her head and flinging it towards him. It hit him in the chest. He caught it before it fell to the ground and returned her grin. He tossed her sweater into the hamper, then rounded the bed to pull her to him, immediately settling his hands on her naked waist as he captured her lips with his own.
Kate melted into him, her fingers moving to undo the buttons of his dark blue shirt. Soon, they were left in just their underwear and moving to lie on the bed. Kate laid on her back, pulling Castle on top of her, relishing the feel of his heated, naked skin pressed against hers.
Castle kissed down her neck and over her chest, careful not to leave any visible marks. He'd quickly learned his lesson with that one. But there was no rule that he couldn't leave marks on other, non-visible areas of her body. He grinned as he ran his lips over the slight hickey just below her breast, left there after a particularly heated encounter a few nights before.
"Castle," Kate gasped as he returned his attention to her breast, teasing the puckered, rosy tip with his lips, then tongue. The roughness of his tongue countered with the softness of his lips made Kate's hip buck in response. She moved her legs, wordlessly encouraging him to settle his pelvis between her thighs, their groins separated only by the thin silk of his boxers and the light cotton of her panties. Kate groaned at the feel of his rock hard length pressed against her center and wrapped her legs around his waist, pulling him closer.
Castle's hips moved rhythmically, creating a delicious friction against her clit. Kate pressed her hips forward, craving more. He stopped suddenly, pulling back and shuffling downwards. Her groan of protest turned into one of appreciation when he hooked his thumbs into the sides of her simple black boy shorts and pulled them down. Kate lifted her hips to assist him as he pulled them all the way off, tossing them carelessly to the floor.
He moved to re-cover her, but Kate stopped him. She reached down and tugged at his boxers, managing to get them halfway down his thighs before he had to take over and kick them off. Before returning to his previous position, Castle reached over and slid open his nightstand drawer, feeling around for the cardboard box. He grabbed it and pulled it out, growling when he realized it was completely empty. He rose to his knees and cursed.
"What?" Kate asked, lifting herself up on her elbows.
Castle flipped the box that had previously held the condoms upside down, showing that it was empty. "I didn't realize we'd used the last one," he explained. "Do you still have any in your purse from when we went to the Hamptons the other weekend?"
"Yeah," Kate groaned, dropping back to the bed. "But my purse is at my apartment."
Castle sighed in frustration, tossing the empty box onto the nightstand and mentally kicking himself for not picking any up that morning when he'd been at the store. "I'm sorry," he said, attempting to move to lay on his side beside her.
Kate stopped him, locking her legs back around his waist. "Castle, I'm too horny to stop now. Just fuck me."
He was stunned. Even after months of being in a relationship, Kate had always insisted that they use a condom even though she was on the pill. "Are you sure?" he asked, exhilarated and more aroused than ever, if that was even possible.
"Yes," Kate cried out, drawing out the sound and tugging him forwards with her strong legs.
He pushed his groin forwards, his length immediately drenched with her wetness. "God, Kate, you're really into the idea of me inside you with nothing between us, aren't you?" he breathed into her ear as their hips gyrated in a steady rhythm, his hardness rubbing against her clit with each movement.
Kate gasped, her fingers digging into his biceps. He was right. Never before had she been with a guy who wasn't wearing a condom. Never before had she trusted a guy enough to come inside her. And never before had the thought of letting a guy do just that made her ever muscle quiver in pure anticipation. "Yes," she whimpered. "Please, now, I need you inside me. Just you." She pulled his head up for a kiss, attacking his lips and tongue as he repositioned himself at her entrance. She sobbed in relief as he began sinking into her, inch by inch, until he was fully embedded inside her. "Oh, god," she gasped, the feeling of him, just him, so deliciously sinful and right. "Castle, move," she demanded after a few seconds of non-movement.
Castle did so, but slowly. He'd barely gotten inside her when he'd had to stop and take a breath for fear that he'd lose control just by feeling her wet heat gripping him so tightly, so perfectly. "You feel so good."
Kate panted, making those little mewling sounds that she made when she was close to coming that drove Castle insane with arousal. Needing to draw the moment out, he paused in his thrusts and maneuvered to lay on his back, Kate straddling him. He never left the heated sheath of her. Kate braced herself above him, palms against his chest as she lifted herself up and down on his erection at a steady pace.
"Castle, I don't know how much longer I can hold on," she groaned, her movements getting quicker and more uncoordinated.
"Don't," he replied, moving his fingers between her legs to rub against her clit. "Don't hold on. Come for me, Kate. Let me feel you." He circled once, twice, three times, and she threw her head back and came on a long, low moan, her thighs clamping around his hips as he followed her over the precipice. Her inner walls milked him as he came inside her, her name a steady resonance on his lips.
Kate crumpled onto his chest as they both recovered from their extreme highs, breathing quick and unsteady. Castle felt his erection softening, eventually forcing him to withdraw from her. Kate rolled onto her back beside him and he followed, propping himself on his elbow next to her. He brushed back a stray curl and kissed her nose, then her lips. "God, you're so beautiful," he said. And it was true; never before had he seen a more beautiful sight than Kate Beckett, flushed with post-coital bliss, that look of sublime satisfaction and content written all over her face. He could try for a hundred years to perfectly describe that look with the written word, but he'd never be able to come close. Ever.
Kate kissed him, pressing her legs together at the strange feeling of his essence inside her. She could feel a bit of it trickling out of her, the feeling both elicit and exhilarating.
"I need a shower now," she murmured several minutes later. "Wanna help me get all clean?"