She honestly should have seen it coming.

The stupidly childish promise they had made to one another at the tender age of eight had been in the back of her mind for weeks (and if she were being completely honest with herself, months even).

They had been playing in the sandbox together, building their own castle with tiny shovels and buckets, and Emma had broken into tears when Neal, the bratty boy from the grade above her, had called off their "relationship" (obviously he was too old to be seen with babies that still played in the sandbox).

But Killian had been there for her in an instant, wrapping his small arms around her crying form, making threats towards the other boy all the while. His tiny fists clenched in anger, desperately trying to calm his best friend down, gentle voice soothing her as best he could.

And, taking his small hands in hers, promised her that she'd never be alone - that if they had both not married someone by the age of thirty, they would be each other's forever.

They pinky promised, little fingers wrapping tightly together, the tears still drying on Emma's innocent face.

That had been years ago, the day still fresh in Emma's mind. It was the day that Killian's status changed from friend to best friend. They had endured everything together - awkward teenager years, prom, graduation, college, even first jobs. Their age had changed nothing between them, their friendship still as strong today as it was back then.

That was until Emma realized that her thirtieth birthday was quickly approaching - and she was currently husband-less (not even a prospect in sight, her nights instead usually spent curled on the couch with a good book or over at Killian's for their weekly Netflix night).

So when Killian had slid the velvet box toward her at her birthday dinner (which honestly felt more like a date than it should have - roses, flickering candles and soft music), Emma's stomach lurched, mouth going dry at the anticipation of what was to come.

He actually appeared nervous and, for Emma, that had made it all the more difficult.

She had been trying for years to deny her growing attraction to her best friend but she wasn't fooling anyone. When Killian had almost married his college sweetheart Milah, Emma had been miserable for months, locking herself up inside her tiny apartment and avoiding the happy couple at all costs.

She didn't realize until years later why that time had affected her so much.

She had feelings for her best friend.

And all of those moments, those years spent together as nothing but friends, led up to this moment - in the comfort of her dining room where Killian Jones was currently down on one knee, shiny diamond ring in hand.

Emma couldn't help the gasp that had escaped at the sight of the ring (she hadn't expected him to go that far. Hoped maybe, but never expected). Her jaw went slack as he smiled up at her, cheeky grin only slightly covering his current awkwardness, before he licked his lips once and began to speak.

"About twenty two years ago, in the sandbox at our elementary school, I made a promise to you. And for a while, with my almost marrying Milah, I never thought that this moment would come – but perhaps for some reason we were destined to be together. You're the most loyal woman I know and I couldn't ask for a better partner. I care for you greatly, lass, and you're the best friend a man could ever have."

"Killian-" she interrupted before he grabbed her hand with his free one, lacing their fingers together, his thumb rubbing soothing circles over hers (and the supposed calming gesture only made her more nervous).

"Shh, love, and let me properly propose."

He exhaled shakily, shifting uncomfortably from his spot on the floor in front of her and Emma felt the tears beginning to prick her eyes at the elaborate measures he had actually went through for her.

"Will you become my best friend for life, my other half, my wife?" Unlacing their fingers, he reached up to wipe away the tear that ran it's way down her flushed skin, thumbing at the apple of her cheeks with a smile. "Emma Swan, will you marry me?"

His eyes were hopeful and expectant, more than she had ever anticipated, and her heart leapt at the thought of spending the rest of her life with him. But she knew that decision would be selfish, denying him of the things in life everyone should have, even denying herself (because as much as she was in love with him, Emma knew that the feelings weren't reciprocated. It would only bring her pain to be married to the man she loved, who only just cared for her in return. Emma Swan wanted love, not friendship).

"Killian…" she began with a sniffle, forcing a smile his way. "You deserve love, your own happy ending. You deserve so much more than me. As your friend, I can't let you go through with this."

After a moment of silence, the ends of Killian's mouth tilted up into a grin as he shook his head in disbelief. "Love, nothing would make me happier than to make you happy. You know I've never broken a promise and I bloody well don't intend to start now. So quit being so stubborn and just agree to marry me already!"

His tone was playful, the best friend she had grown to love. And while this should feel like a mistake, Emma only weighed the pros in her mind. Glancing from his blue eyes down to the ring and then back up to his face, she knew there was no getting out of his one.

If Killian made a promise, he was going to keep it no matter what; he was in this for the long haul.

"Okay," she breathed out with a nod, allowing him to slip the ring onto her finger before pulling her into a bone-crushing hug. With her lips close to his ear, she whispered, "I'll marry you."

(If it was said to convince more herself or him, she didn't know)

They were married two weeks later in a simple ceremony at the town hotel.

A few close friends were in attendance, Emma's college roommate Mary-Margaret by her side as maid of honor. She wore a simple white dress, with soft golden curls spilling over her shoulders, and the pearls Killian had given her on her sixteenth birthday.

She was surprised to see tears in his eyes as she made her way down the aisle towards him. He looked gorgeous in his black tuxedo, messy hair his signature look, as he waited at the end for her. Feeling his large hands slip into hers only helped to confirm that this was actually happening.

She was marrying her best friend (and surprisingly feeling no regrets yet).

The ceremony went by in a blur, vows repeated and rings exchanged, smiles and laughs abound. It wasn't until the end was near that Emma felt tense, the weight of what had just occurred fully on her shoulders.

Their lips finally met in a kiss to seal the deal, smooth lips sliding across the other, his hands reaching up to cup her cheek and pull her closer (it wasn't the first time she had kissed him – he being her first kiss when she had turned the free-spirited thirteen), but the way his lips felt against hers wasn't exactly what she had been expecting.

They kissed for what seemed like hours; his tongue even finding it's way inside her mouth to coax hers out. It was like an explosion inside, fireworks even - until someone coughed, causing the pair to jump apart as if they had been caught doing something wrong.

And if the look on his face when she pulled away was any indication (his fingertips ghosting his lips were hers had just been), it was definitely more than Killian had been expecting too.

The rest of the evening proceeded with haste, a simple reception party set up for the two at Mary-Margaret and David's house. Sappy speeches were made and laughter was rampant among the guests, and when the wine came out, all bets were off. Amidst all the chaos, somehow Killian had managed to sweep Emma off to the middle of the makeshift dance floor, their wedding song playing as he slipped his hand around her waist and pulled her close.

They had hardly spoken since the kiss, but there was nowhere Emma would have rather been than in his arms, her forehead resting in the crook of his neck, hand placed gently upon his rapidly beating heart.

The dance ended as quickly as it had begun, more people approaching to congratulate them before whisking them off in different directions, leaving them to only steal glances across the room from one another every so often.

When the clock rolled to midnight, Emma kissed her maid of honor on the cheek, bidding them goodnight and thanking for the kindness shown. The brunette had given her a sly wink, insinuating that she have a fun night and to attempt to get some sleep.

Her cheeks had grown red in embarrassment at her friend's suggestion and the silent ride back to his (god, their) apartment was more awkward than words could even begin to describe.

Killian was her friend, no matter how she felt for him, and that was apart of the guidelines for their agreement. They didn't agree for love, but rather for comfort and companionship, the best friendship two people could have.

(She'd be lying if she said she hadn't thought about this night, about what would come about when they were to consummate their marriage. No, Emma thought of it – often. Thought of running her hands through his dark hair, nails scrapping against skin, hips perfectly aligning.)

They got ready for bed in silence, as if routine, changing into their night attire without speaking a word. She wanted to talk, to figure things out, to know exactly what had been going through his head since the kiss (to know if he already regretted his decision).

He was speechless when she exited the bathroom, sexy lingerie leaving little to the imagination (and she inwardly made a note to thank her friend Ruby for the gift). His fists were clenched tightly at his side and Emma swayed her hips from side to side as she approached him.

"Emma," he breathed when she finally stood before him, walking them both back towards the bed. "Love, we don't have to do this is you don't want to. I don't want to make you uncomfortable."

(He had absolutely no idea how long she had wanted him like this – nervous and full of desire and completely hers)

"Now what kind of wife would I be if I couldn't please my own husband?"

His knees hit the bed and they tumbled down together in a pile of limbs, her skin sliding against his and he hissed at the contact. Pulling her closer, her legs fell apart to straddle his waist, and Killian squeezed his eyes shut tightly when her core thrust against his already growing erection (as if he shouldn't be feeling this way about his best friend – now wife - trying to reign in his hormones that were only thinking about what it would feel like to finally be with her).

"It's okay, Killian," she soothed, fingers running through his messy locks (finally, finally – her mind screamed), scarcely covered breasts pushing up against his bare chest. "I don't mind."

He relaxed a little at her admission (and Emma internally breathed a sigh of relief, her body humming with pure pleasure at the thought of being able to finally sleep with the man she had dreamt about for years).

"In fact," she began, nails now scrapping against his chest, her mouth planting open mouth kisses all the way up to his neck. She stopped just below his ear, taking the lobe into her mouth and nibbling lightly before speaking softly. "I kind of want this."

Her hips swiveled against his, rutting lightly and a moan slipped through her mouth at the feeling of him against her. He gave a few experimental thrusts against her, the cloth of his boxers and her panties rubbing against them, yet still separating too much. Somehow she managed to give a dark chuckle, quickly turning into another groan that left her panting against his skin. "And apparently you do too."

At her words, something inside Killian snapped, holding her steady against his form to flip them over, pushing her deep into the mattress, hair spilling around her like a golden halo. With a low growl, his lips finally found hers, clothing quickly removed in a clash of limbs and teeth and tongue.

The drag of his mouth against her skin had her wet and wanting within minutes, his expert tongue brushing against her hardened nipple, swirling around her belly button and then finding her slick below, moist and ready for him. A muttered "I've always wondered how you would taste, love," pressed against the skin of her thigh where he was nipping at the flesh.

She had always ached to know how he was in bed and, needless to say, he didn't disappoint. In mere minutes, an embarrassingly short amount of time, he had coaxed her up to the edge with only his mouth and ultimately over that golden tipped peak that had her gasping and writhing beneath him, fingernails digging into the skin of his back and her feet planted firmly on the mattress.

Once again, his mouth found hers and she tasted the tanginess of herself on his tongue. Her heart was beating swiftly inside (not just from the earth shattering orgasm he had just given her but also from the fact that she was about to have sex with her best friend, something she had dreamed of since the very first moment he had aroused her, stirrings inside that made her want him as more than just a friend).

And when his cock nudged at her entrance, Emma whimpered in eagerness, his mouth latched to a perky nipple, licking and nipping and sucking the bud between his teeth. Suddenly, he released her breast with a wet plop, finding her lips once again for a soft kiss.

"Emma," he whispered, their sweaty foreheads pressed tightly together as their bodies almost melted into one. His voice was uncertain, questioning, making sure that this was all her decision, that it was something that she truly wanted.

Wrapping her legs around his waist and hooking her ankles at his lower back, he slipped inside her a bit, causing them both to gasp. Emma nodded eagerly, her fingers still in his hair as she replied curtly. "Just do it, Jones."

And then - finally – they came together as one. He filled her, completed her, and made her feel something that she'd never felt before. The burning ache that had first hit when he had abruptly pushed inside of her quickly blossomed into pleasure, building the ache once again low in her belly.

The push and pull was better than she could have ever imagined, the rough drag of his cock against her inner walls pulling the string inside taut, like a bow ready to explode. He grunted with each thrust, holding her closely and whispering loving words against her skin. It wasn't long before she was crying out, urging him to move faster, for more, god, more.

And when his finger sough out her aching clit, she found that peak again, gasping and panting in ecstasy as her walls clenching around him helped him to go over the edge as well. They lay there, breathless and boneless, completely sated in each other's arms.

Turning on her side, Emma gave him one last kiss, a soft goodnight against his flushed skin. He hummed in reply, tucking the hair that was matted to her sweaty forehead behind her ear. She settled back against Killian, him spooning her from behind, and sleep quickly tried to overtake them both.

When he seemed sure that she was asleep, Killian couldn't help but place one last kiss to her skin, his mouth meeting her shoulder. And even in the phase of almost slumber, Emma was certain that the words of "I love you" had been placed against her skin, a mark, a promise.

Then, smiling, she fell asleep in the arms of the man that finally loved her in return.

He woke up in bed alone, the smell of bacon wafting throughout the apartment, and Killian slipped on his boxers before following the scent to the kitchen where Emma had busied herself making breakfast.

She turned around at the sound of him approaching, the biggest smile she had ever given him consuming her face. "Look who finally decided to get up."

Killian gave a chuckle, settling himself onto the barstool, hands folded up under his chin. "Well someone kept me up half the night."

Emma grinned, setting the plate of eggs and bacon down on the counter in front of him, addressing her husband with a wink. "You sure weren't complaining then."

The twinkle in her eye was undeniable and her face softened a bit in his presence. But the knot in her stomach was still twisting and Emma knew what had to be done.

Noticing her sudden uneasiness, Killian set down his fork, wiping his mouth with the napkin and clearing his throat. "Emma-"

"I think we need to talk," she quickly interrupted, plopping down on the barstool next to him. Her hands threaded together and she twisted the shiny ring on her finger in worry. "About everything that has happened. I heard what you said last night. Did you mean it?"

Swiveling his stool towards hers, he unlatched her fingers, bringing them up to his mouth to place a soft kiss to the tips.

"Love, I meant every word I said, every action was true. I've been denying myself so long because I always wanted to put your own feelings before my own, because I didn't want to risk our friendship."

A jolt of pleasure and surprised rushed through her blood, heart rate increasing at his words. He cared – no, he loved her. All this time, both had been denying what they were truly feeling, rejecting themselves from the pleasure and peace they could have experienced earlier if they had just let themselves.

Biting on her bottom lip, she exhaled a sigh of relief. "When did you know?"

"When we were eight."

"The day we made our promise?"

"Aye. I knew then that I wanted to spend the rest of my life with you."

That long. He had loved her that long and she had absolutely no idea. This whole time she had thought that she was the only one with feelings, that it was completely one-sided and hopeless. But here he was, smiling in their kitchen the morning after consummating their love, holding her hands and kissing her as if she were the most precious thing on earth. And, despite the fact that they had waited so long to do so, it was all worth it.

Spreading his legs, he pulled Emma off the stool to stand between them, both of his hands going to cup her face, bringing her lips down to meet his. The kiss was short but they both pulled away breathless, foreheads pressed firmly together. "I love you, Emma Swan."

"Jones," she corrected, her thumb running across his bottom lip. "It's Emma Jones now. And I love you too. For my whole life."

"For our whole lives," he promised, pulling her into his arms, lips sweetly finding each other once again.

Killian Jones had made two promises to Emma during their time together. The first was an innocent promise of marriage, of always being there for each other, one that had now been fulfilled. The second promise was one of forever – of a lifetime spent together with her by his side.

And it was one that he was intending to keep. After all, Killian Jones never broke a promise.