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Part 1 of JJK x Taylor Swift Regency AU
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Published:
2025-02-23
Updated:
2025-11-07
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156,411
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14/17
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Guilty As Sin?

Summary:

Lady Ainsworth has never been the type to indulge in frivolous fantasies of love. She has long resigned herself to a marriage of duty rather than passion. However, when she meets Lord Kento Nanami, a reserved and devastatingly handsome Viscount returned from a long stay abroad, she begins to understand the meaning of temptation.

Nanami is a man of discipline. His every step measured, his words few but cutting in their precision. And yet, when his sharp eyes meet hers across a ballroom, he feels the weight of a desire neither of them dares to name. It is improper. It is inevitable.

When the season's most eligible suitor Duke Gojo begins courting her, Nanami tries to stand aside. But they share stolen glances at dinner parties. Their hands brush as they reach for the same books in the library. Their conversations linger a moment too long. Every touch, every shared breath, is a confession neither is brave enough to voice as propriety must always rule.

Their romance is not forbidden yet too dangerous to be spoken aloud, and yet, neither of them can resist its pull. They are guilty not of sin, but of wanting. And that, perhaps, is the greatest crime of all.

a slow burn, friends to lovers fic

Notes:

Hey besties, happy new year. I'm backkkk with a new story. You may be asking what about the other one and well...after careful consideration, I decided to put it on hiatus because writing a Christmas story in February wasn't working for me. So 12 Days will return around November and in the meantime, I'll be working on other projects including this one :)

(See the end of the work for more notes.)

Chapter 1: Prologue: A Dance with Fate

Chapter Text

London, 1812

The grand ballroom of Lord and Lady Fitzwilliam's estate glittered like the night sky, awash in the golden glow of a thousand candlelit chandeliers. The high, vaulted ceilings bore intricate frescoes of cherubs and Grecian goddesses, their painted forms frozen in eternal revelry. The scent of beeswax, jasmine, and fine French perfume clung to the air. Where it mingled with the soft strains of the music being played by the orchestra tucked behind velvet-draped alcoves.

It was the start of the season, and the ton had gathered in all its finery to witness what would surely be an evening of whispered intrigues, swift-footed gossip, and carefully calculated courtships.

Ladies adorned in patterned heavy silks and embroidered muslins of the palest pastels floated gently through the room. Their skirts sweeping the polished marble floors and delicate gloved hands grazing the arms of chaperones and suitors alike. Gentlemen, made handsome in dark coats and embroidered waistcoats, stood in small groups with glasses filled with amber liquid. As they murmured about politics and horses, their eyes inevitably wandered toward the season’s most sought-after debutantes.

Including Lady Ainsworth, who was this season's diamond. A title bestowed upon her most graciously by Her Majesty. A title that set every gaze in the ton upon her. She was a vision tonight. Her gown, a masterpiece of craftsmanship, shimmered in the candlelight. It was a most delicate confection of the palest blue, its fine muslin overlay embroidered with silver thread in intricate patterns. A satin ribbon, tied just beneath her ample bust, accentuated the empire waistline. Around her throat, a single strand of pearls glowed softly, complementing the luminous quality of her skin and the pearls in her tiara. She was dressed to be seen, admired and envied.

Yet she felt as though she was little more than an ornament made to be displayed. As such, she stood off to the side of the ballroom. Despite being practically invisible in her alcove, her posture was impeccable. Her every movement a studied grace. She had long since learned that in such company, one must always be aware of how they were perceived even if no one else is looking. A laugh must never be too loud, a gaze never too lingering. It was a game, one she had played for years. And yet, tonight, a strange restlessness stirred within her.

Maybe it was because tonight, it had all suddenly become real. The fanciful whimsies of childhood were being replaced with the harsh reality of duty, marriage and motherhood. And as she stared at the debutantes fluttering their eyelashes and laughing demurely, she felt isolated.

A million questions raced through her mind as she looked at the joyful crowd. Was everyone else okay with their duty except her? Was she the only one who wanted more? Could there ever be more for her? She was the daughter of a Duke. Even if she were not the most handsome, many would still vy for her hand. Be it for her hefty dowry, the desire for an accomplished wife or her father's connections, none wanted her for the right reasons. Or at the very least, the only reason that mattered, love.

Her parents had been a rare love match but most of her siblings had not been so fortunate. Her elder siblings Edmund and Arabella had all been married off for one advantageous reason or another and Lady Ainsworth knew what awaited her. Yet, though she would never admit it, she longed for excitement. For a handsome man to swoop in and sweep her off her feet.

It was then that he arrived.

Viscount Nanami entered the ballroom with the quiet command of a man who had no need to announce himself. There was no ostentatious display, no flourish to his step. Only the weight of his presence. The kind that drew the eye and stilled conversations mid-sentence. He was dressed simply, though in a manner no less elegant than those around him. A black tailcoat fitted with perfection, a crisp white cravat, a gold watch chain glinting against the deep navy of his embroidered waistcoat. His simplicity drew attention to his striking physical features and as her eyes followed the path he was making through the room, Lady Ainsworth couldn't help but think him to be remarkably and devastatingly handsome.

But it was not his attire or his features that held her captive. It was the man himself.

He was not like the other gentlemen of the ton. As he made his way through the room, there were no phony smiles, no eager attempts at pleasantries. His expression was solemn and his gaze sharp, as he surveyed the room with an almost detached interest. As though he found it all vaguely tiresome. As though he was bored of it all and simply here because it was expected of him.

As he stood speaking to some Lord or something of the sort, he happened to look up. And as his hazel eyes met hers across the ballroom, she felt her breath catch in her throat.

A spark of interest flickered in his eyes as the moment stretched between them. Too brief to be improper, too charged to be ignored.

Pulling her gaze away, she murmured to Lady Ieiri, her closest friend and lady in waiting, "Who is that?”

"Viscount Nanami," Came the whispered reply, "He has recently returned from the Continent.”

Lady Ainsworth had heard of him before but she'd never seen him prior to today. He was, of course, talked about in society but much of it was only speculation. Yet she asked anyway, “Do you know much about what he is like?”

Shoko shook her head, “Only that he is a man of honor. He does not entertain idle gossip, nor does he seek the company of the ladies." A pause, "Or rather, he did not until now."

Lady Ainsworth turned back toward him, only to find him already approaching. The crowd seemed to part effortlessly for him, as if even the ton’s most ambitious mamas knew better than to throw their daughters into his path.

Then, before she could gather her wits, he was standing before her.

"Lady Ainsworth," He said. His voice, a smooth yet low timbre, sent an unfamiliar thrill down her spine. He bowed precisely and formally, though there was something in the way he held her gaze as he straightened that set her heart racing.

"Viscount Nanami," She replied demurely, dipping into a graceful curtsy.

"Would you do me the honor of a dance my lady?"

She hesitated for a mere fraction of a second, but that moment was enough for her to know that she should refuse. This man was not like the others. There was no charm in his tone, no flattery to his words. Nothing except a subtle interest and quiet intensity that threatened to unravel the acceptance of her fate that she'd forced herself to achieve.

And yet, despite her better judgement, she extended her gloved hand.

"The honor is mine, my lord."

As his fingers closed over hers, firm yet impeccably restrained, she felt a twinge of what could almost be described as hope blooming inside.

The orchestra swelled, easing into the first strains of a waltz. A dance which had been rather scandalous and had only recently been deemed acceptable in polite society due to its nature. Even now, it was met with quiet disapproval from the conservative matrons who refused to learn it and instead sat fanning themselves at the edge of the ballroom. To dance the waltz was to step dangerously close to impropriety, for it required a closeness between partners that no other dance permitted.

Lady Ainsworth was no stranger to the waltz. She had danced it before, always with the appropriate distance between herself and her partner. Like a proper lady of genteel breeding and refinement, she was always mindful of where her gaze should rest, of how long her hand should linger. But as Viscount Nanami placed one steady hand at her waist, and his other clasped hers deftly, something inside her shifted.

It was the weight of his touch. Not improper. Rather so firm it caused a heat where he touched. It was the scent of him, warm and clean, tinged with the faintest hint of sandalwood and something darker, something richer. It was the way his eyes found hers, his gaze unwavering, as if he, too, sensed the air thickening between them.

He moved with a practiced ease, expertly guiding her into the first sweeping turn. Their steps were done precisely, as dictated by the rigid formalities of the dance, yet beneath it, there was something else…something unspoken.

“Your waltz is quite perfected, my lord,” She murmured. She'd somehow managed to keep her voice even, though her pulse was not.

“As is yours, my lady,” He replied. His tone was polite and to her surprise, devoid of the empty flattery she so often received.

They fell silent again and Lady Ainsworth was disappointed. She had wanted to hear his voice more. Even if it were to merely comment on the evening or the music or some other trivial matter. Instead, he was silent, his focus entirely on the dance, on the way they moved seamlessly in unison. It was unnerving yet oddly thrilling.

The candlelit chandeliers above cast their golden glow over them as they turned. The light gilded the Viscount into a sight that was almost otherworldly. His jaw was set in a solemn line, but she could see that it did not come with ease. Similarly to her, there was restraint and careful control in his expression. They had both mastered the art of composure, yet beneath the surface, something flickered in two of them.

The music swelled, and as they dipped into a turn, she brushed a fraction too close. And as her breath hitched from their close contact, she felt the smallest, almost imperceptible tightening of his hand at her waist. It lasted no longer than a breath, and yet it sent a shiver down her spine.

This was not how it was supposed to be. A dance was a formality, a display, an elegant performance put on to attract suitors. But this, this was something else entirely. She felt seen as something far more dangerous than what she was: a woman that was desired. His gaze that never left her face seemed to echo that he saw her as such.

“You are staring, Viscount,” Lady Ainsworth whispered, attempting to infuse her voice with the teasing lilt she used with other gentlemen.

Viscount Nanami did not smile and truthfully, it made her heart fall as he casually replied, “Am I?”

The words were quiet enough that only she could hear them over the waltz’s melody.

“Yes you are my lord” She said, “It is most improper.”

His thumb stroked her waist softly, a small movement against the fabric of her gown, “Then I shall endeavor to be more discreet.”

But he did not look away. Instead he kept his gaze on her and for a second, it seemed almost like he softened. Shaking it off, Lady Ainsworth tried to ignore the steady pull she felt towards him. Heat was curling in her stomach and it was unfamiliar and wholly unwelcome.

She wished then that she could step back. Put space between them and remind herself of her duty enough that he'd become a passing distraction. But the dance dictated her movements, and propriety required her to be respectful, even as everything inside her begged for escape. Even as she felt overwhelmed by these feelings she'd never had before.

As the final notes of the waltz played in the air, the moment between them stretched until they realized the dance was over. He released her hand first and the absence of his touch was a kind of loss that she was unfamiliar with. Then, with practiced elegance, he stepped back, offering her a bow so perfect that it might have been rehearsed a hundred times before.

She curtsied in return, the hem of her skirts whispering against the floor as her heart pounded in a way it never had before.

“My lady,” He said, his voice steady and even as if nothing at all had passed between them.

“My lord,” She replied, tilting her chin just so.

With a final look, he turned and disappeared into the crowd. And as he walked away, she knew with startling certainty that something that could not become undone had happened to them. With one dance, everything had changed and whatever had just begun between them, it would not end easily.