The idea of spending the next eternity with Richard Castle would have horrified her once, probably would have pushed her to kill him for not letting her die in peace back when he was just a supposed asshole playboy following her around for the sake of a story that has long since been told. But while it still scares the shit out of her sometimes, the idea of forever with him wouldn't have sounded so bad before he'd saved her life that night in the freezer, and she no longer minds the prospect of it so much now either.

She'd been at risk of loving him then and she was under no illusions over the depths of her love for him now, how that love blossomed like a brilliant flower through her chest, vibrant vines twining around her ribcage, petals tickling at her stationary heart, her useless lungs.

Within these three months spent away - the "transition period", as he liked to call it - in a secluded villa on the island of Cyprus, she tends to the bloom of it, lets it grow, has stopped trying to smother it.

Though, it had taken her a while to even think about the development of her feelings for Castle, to focus on anything other than her new form of living, the foreign needs and requirements that came with being vampiric, the restrictions. To his credit, Castle proved to be an excellent teacher, patient and understanding, helping ease her into every adjustment step by step until eventually they were able to spend entire days around actual humans and the urge to taste blood on her tongue no longer overpowered her control.

"I knew your control freak tendencies would benefit you, Beckett," he'd teased her as they'd walked through a marketplace in the middle of the day and Kate had rolled her eyes, startled him with the playful nip of her teeth to his jaw.

"You're just lucky I prefer my meals in the form of smoothies these days," she'd hummed, snagging his hand and twining their fingers, meandering through the gorgeous island with him as if they were just two people simply on vacation, on the cusp of being more.

At least part of it had been true.

Hearing the thoughts of those around her, the dull murmurs of minds, insight into each and every human being within a short radius eventually helped soothe the acquired urge to attack too. Though, at first, it had driven her completely crazy, her compartmentalization skills shot to hell, but Castle had coached her through it, soothed the onslaught of thoughts in her head that weren't even her own.

Within two weeks, she's able to sort through them, shut them down if she has no desire to listen. There is one mind she's incapable of reading though, the one she wants to know more than any other.

"Powers don't usually work on… mates," he reveals one night, sitting beside her on the edge of the infinity pool beneath the blanket of midnight blue overhead, the twinkle of the stars.

Kate chokes on her own breath. "Shit-"

"Ouch, Beckett," he huffs in offense, but he laughs at her as she buries her face in her hands in embarrassment over his only logical explanation.

"Why do I even have this… what do I even call it? A special gift?" she questions, but Castle smirks in response.

"Super power," he amends, earning the light smack of her hand to his arm. "And I don't have the answer for that. From what I've learned, certain people are just reborn with them, but seriously, can you imagine once we get back to the city, to the NYPD? Interrogating suspects will be as easy as breathing."

"And avenging my mother's death… it finally feels possible," she murmurs, aware of the stiffness that invades his shoulders, climbs his spine, and Kate sways into his side. "It's not so dangerous anymore, you know that."

"We don't know that," he argues quietly. "For all we know, they could be like us, or have people like us working for them. The danger doesn't disappear just because you're less vulnerable to violence. I'm not saying I want you to give this up, just… promise me we stay partners, that I continue to have your back. That we do this together."

It's the first time she leans in, brushes her lips to his mouth in a kiss that is tender but resolute, a soft caress and a seal of certainty, a promise. A last first kiss.

"Partners, Castle. Always."

By the time their return date to New York begins to grow near, she's fallen into the habit of spending her nights in his bed – not sleeping, she had quickly learned that vampires do not possess the privilege of rest, much to her chagrin – and lying against him as the sun crests the horizon, bleeds its light onto the bed sheets, trailing warmth along her naked skin.

"Don't ever regret this," she mumbles on their final morning in Cyprus, earning the downwards tug of his brow in question, but it doesn't take him long to understand, to discover her train of thought.

"I wanted you to have the best life possible, as a human," Castle states, his reasoning unwavering, but she fits her palm to his jaw, stains her smile to his mouth.

"Castle, it wasn't until I met you that my life became extraordinary," she confesses in this moment of vulnerability, naked and tangled around him, but feeling braver than ever before. "I know it took awhile for me to admit that, but it's always been true."

"Kate-"

"I don't regret it," she whispers, shifting her body over his, easing him onto his back and straddling his hips, draping her torso atop his, aligning the dormant muscles of their hearts, the paled flesh of their scars, and cradling his face as he splays his palms over the wings of her shoulder blades. "I love you back."

He rises into the touch of her lips, devastates her mouth with a kiss that leaves her breathless, that floods electricity and heat through the cold, empty cavern of her body that never fails to come alive for him.

She arches into him when he flips them over, pinning her down to the mattress with the twine of their hands above her head, and catches his bottom lip between her teeth before she speaks one last truth, before she stops speaking altogether.

"And I wouldn't change it."

There's no one else she would rather spend the entirety of her forever with.