Fate/Charm of

the Devil Fae

This fic is inspired by Sticky Situation by  Professor Quill,   In Bloom by Flight of Fancy,  and to a certain extent Benefits of Saving a Veela by WD_ONeill . Please check them out.

Story Starts

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Ch. 0.1 Prologue

Quenching of the Sword

Disclaimer: Everyone here is at least 18 years of age. In Japan, students are typically 18 years old during their last year of high school. So all scenes of a sexual nature were done between consenting adults.

But to be safe, let’s add an addendum: this is a major AU. After Senior High School, students generally go to an academy for one to three years to take general subjects, think honestly about what they want, and prepare for higher education, or take vocational courses. This will take place during that period.

Shirou’s base level ' Charm’ is more akin to a Veela’s aura; it lowers the inhibitions of people who are attracted to Shirou, but ultimately, it’s up to them whether they want to act on it. It also depends on their general level of promiscuity.

In this story, both Sakura and Rin are fraternal twins, and I’m not going through the Illya-is-a-legal-loli route, nor will I ever—not that there’s any wrong with young-looking or petite adults.

Disclaimer 2 (For Patreon Staff): To avoid getting this chapter blocked and to skip the need to appeal. There will be no incest in this story. This chapter and the following chapter will involve Shirou x Sakura & Shirou x Rin, they just so happen to be in the same room. Nothing sexual will cross between Rin and Sakura.

Even with her commanding order still hanging in the charged air between them—that imperious demand that he fuck her now—Shirou could clearly perceive the embarrassed flush spreading rapidly across Rin's face. The colour bloomed from her cheeks down the elegant column of her throat as he carefully manoeuvred them, rolling her gently onto her back with deliberate care whilst maintaining their intimate connection. He moved slowly, conscious of every point where their bodies touched, where they remained joined.

Their bodies stayed connected throughout the shift, not a single inch of separation, and her legs instinctively wrapped more securely around his lower back in response. Her ankles locked together with surprising strength, as if to prevent any possibility of him withdrawing, of ending this moment before she was ready.

The way she'd commanded him moments ago—demanding and imperious, so quintessentially Rin even in this vulnerable position—hadn't quite managed to mask the genuine vulnerability lurking beneath that carefully maintained veneer of authority. He could see it in her eyes, in the way her breath hitched when he settled his weight more fully against her.

Shirou studied her with an intensity that made his chest physically ache with the overwhelming weight of his feelings. She was his best friend, had been ever since Runeas had answered that desperate call eleven years ago, arriving to find him broken and cursed in that hospital bed. Through everything—the curse, the isolation, the fear—she'd stayed.

He traced his hungry gaze across every minute detail of her face and body with the reverence of a man memorising something precious: the dark, lustrous hair that normally framed her face so neatly in her signature twin tails was now completely loose and splayed in wild disarray across the rumpled futon beneath her head, spread out like a dark halo.

Those bright aquamarine eyes—framed by impossibly long dark lashes—held such fascinating complexity that he could happily lose himself in them for hours. Intelligence and passion warred constantly beneath their surface, along with something softer now, something trusting that made his throat tighten.

Her beautiful face held his complete attention: the elegant, sharp curve of her high cheekbones that gave her that unmistakable aristocratic air, her soft lips currently pressed into a stubborn pout that made him want to smile despite the overwhelming intensity of the moment. Even now, even like this, she was trying to maintain some semblance of composure.

His eyes drifted slowly, almost reverently downwards, drinking in every visible inch of her exposed body with deliberate attention. He followed the graceful line of her jaw where it met her neck, lingered appreciatively on her slender throat, and traced the pronounced definition of her delicate collarbone, which stood out beautifully with each gasping breath she took.

Lower still, his gaze caressed her modest breasts—perfectly proportioned to her slender frame—now glistening with a sheen of sweat that caught the lamplight. He watched them rise and fall rhythmically with each laboured breath she drew, each subtle movement sending corresponding waves of sensation rippling through him where their bodies remained pressed so intimately together, her stiff nipples dragging against his chest with delicious friction.

Her flat, toned stomach bore visible evidence of years of dedicated physical training and magecraft practice, the subtle definition of muscle flexing beneath skin with each small movement. His eyes traced downward appreciatively to the gentle flare of her hips where they connected so perfectly—where he remained fully buried within her tight, scorching heat. He could feel every subtle pulse and flutter of her inner walls clenching around him, the undeniable physical proof of her desire matching and amplifying his own until he could barely think straight.

Beat. Beat. Beat.

His pulse thundered in his ears, or perhaps it was hers—he could no longer tell where one ended and the other began.

"ARgh!" Rin moaned suddenly, her voice pitched notably higher than before, a note of genuine surprise and pleasure threading through it. Her back arched slightly off the futon. "Did you get bigger?"

The breathless question hung in the charged air between them, wondering and almost accusatory. Part of her genuinely couldn't tell if he'd somehow swelled even further within her already stretched passage, or if her body was simply becoming hypersensitive to every millimetre of him—more acutely attuned to his presence filling her so thoroughly that even the slightest pulse felt magnified tenfold.

Beat. Beat. Beat.

"Hnnnn," came another moan—involuntary, raw, wrenched from somewhere deep in his chest—as Shirou felt his cock twitch powerfully within her tight heat. The sensation was almost unbearable in its intensity—that responsive flutter of her inner walls immediately acknowledging his arousal, her body answering his with a clenching pulse that amplified the pleasure tenfold and threatened to shatter what little remained of his control.

Lust. Pure, undeniable, all-consuming lust was devouring him now, burning away the last vestiges of restraint he'd been clinging to so desperately. The past few minutes had been an absolute blur, a confused tangle of overwhelming emotions and sensations where everything had spiralled so suddenly, so unexpectedly into this moment of perfect connection.

He'd been holding back earlier with iron determination, acutely aware that this was her first time, terrified of causing her pain or lasting discomfort despite the overwhelming urge to simply lose himself completely in the welcoming heat of her body. But now? Now everything had fundamentally shifted.

Beat. Beat. Beat.

Now that she'd assured him—repeatedly, explicitly, with both words and actions—that this was what they both wanted, what they both needed. Now that he realised with crystal clarity how desperately his own curse-wracked body had been crying out for this specific release, how he hadn't even had a chance to relieve himself properly yet despite how painfully aroused he'd been since first entering his room a few minutes ago.

Beat. Beat. Beat.

He thought back almost distantly to his original plan when he'd closed that fusuma door—just a few private moments alone to take care of himself before going back to his grind of hammer and molten metal. But then she'd arrived with the others, and everything had changed in ways he never could have anticipated.

Beat. Beat. Beat.

'Fuck. Me. Now.' That's what she'd said, wasn't it? Those three words—demanding, giving permission, obliterating his excuses. The green light he'd been unconsciously waiting for, blazing bright through the suffocating fog of his self-imposed restraint and martyr complex.

The temptation to let loose completely was gnawing at him with increasing urgency, clawing at his carefully maintained composure with every fibre of his being, every cell in his body screaming at him to just take what he needed—

Then Rin raised her hand to his face with unexpected gentleness, her palm cupping his cheek, her touch somehow grounding amidst the absolute chaos of sensation threatening to drown him. "Don't worry," she breathed reassuringly, her voice softer now, more tender than commanding. "Everyone agreed to this, Shirou. Runeas, Vivian, Lady Avalon, Taiga—they all approved. This isn't just about the curse. We want this too."

She leaned up despite their position to capture his lips, drawing him down into a tender kiss that was almost shockingly intimate and sweet given their current situation—still joined so completely, his cock buried to the hilt inside her whilst they kissed like this was their first time all over again.

They separated slowly, reluctantly, but Rin's expression transformed dramatically into that knowing smirk he recognised so well, her aquamarine eyes glinting with pure mischief and promise. "Plus, if you perform well today, Ayako did say she wants a turn." Her hand reached out deliberately, slender fingers playing teasingly across his nipples and making him jolt. Her whisper came hot and breathy against the shell of his ear: "Imagine that—a proper threesome between your best friend and her girlfriend, the two of us sandwiching you between us, taking turns riding you whilst—EEEECK!"

Rin's playful teasing was brutally cut off with a sharp, startled gasp as Shirou suddenly pulled back without warning, withdrawing until only his tip remained inside. His muscles coiled tight like a compressed spring before snapping forward explosively in one powerful, punishing thrust that buried himself completely within her in a single stroke. The suddenness and force of it punched all the breath from her lungs—her teasing smirk vanishing instantly as her back arched violently off the futon, fingers scrabbling desperately for purchase against the rumpled sheets beneath her.

'God, she was so tight.' The realisation crashed through Shirou like a physical blow, impossible to ignore or suppress despite everything else competing for his attention. The feel of her inner walls clamping desperately around his length was exquisite torture—slick, scorching heat embracing him with such overwhelming intensity that it threatened to unravel what little remained of his carefully maintained self-control completely.

Each involuntary contraction of her muscles sent bolts of white-hot pleasure coursing through his veins like liquid fire, and he found himself tensing instinctively against the overwhelming sensation, fighting the primal urge rising within him to simply lose himself entirely in the moment and take her with abandon.

The sensation was utterly all-consuming, absolutely intoxicating, and he couldn't help but marvel with some distant part of his mind at how perfectly she seemed to fit around him, how her body moulded to his as though they'd been made explicitly for this joining.

The thought seared through Shirou's consciousness, white-hot and utterly all-consuming, burning away everything else. Every nerve ending in his body was alight with sensation, every inch of her scorching heat gripping him like a vice explicitly designed to drive him mad. He barely registered the sharp sting of her nails digging crescents into his shoulders as he shifted his weight, pushing her down more firmly into the futon.

His free hand splayed possessively across the curve of her hip to hold her steady, fingers digging into soft flesh. He hooked her knees over his forearms with deliberate intent, lifting her legs high against his chest and spreading her wider—opening her more completely—as he began to set a brutal, utterly unrelenting pace.

Each sharp snap of his hips drew broken, incoherent sounds from Rin's lips, her usual careful composure completely shattered into breathless moans and gasps. The obscenely wet slap of skin meeting skin filled the room with lewd percussion, the sound mingling with the increasingly ragged hitch of their laboured breathing.

"Shi—ah!—Shirou—!" His name tumbled from her lips in fractured, desperate pieces, each syllable a breathless plea that sent a fresh surge of dark triumph and burning desire coursing through him like electricity.

Her voice trembled audibly with the impossible strain of trying to hold herself together, even as her body betrayed her completely with every helpless clench and shudder. He angled his thrusts with increasingly deliberate precision, adjusting the angle of penetration as he sought that particular spot deep inside her—that devastating angle he'd discovered that made her thighs quiver violently and her toes curl so tight against his back that he could feel her nails through his skin.

The knowledge of exactly what undid her—where to touch, how to move, what angle made her scream—filled him with a fiercely possessive satisfaction that was almost as intoxicating as the physical pleasure itself.

The scent of her surrounded him entirely, inescapable and overwhelming—clean sweat mingling with something heavier, headier, uniquely and unmistakably her. The musk of her arousal was thick enough that he could practically taste it on his tongue, the scent clinging to the humid air trapped between their moving bodies. He inhaled deeply despite his ragged breathing, losing himself completely in it, in her, in this moment.

He could feel her inner walls clenching around him in increasingly desperate little spasms, her entire body fluttering and trembling as though she might literally come apart at any moment beneath the relentless assault of sensation. That tight, rhythmic pressure of her muscles contracting around his cock threatened to undo what remained of his control entirely.

The sight of her spread beneath him was almost unbearable in its perfection—her chest heaving with ragged, gasping breaths, her lips parted wide on wordless cries of pleasure, her normally sharp eyes now glazed over and completely unfocused with overwhelming want. It was nearly enough to shatter what little remained of his restraint completely, and he found himself teetering dangerously on the knife's edge of losing control altogether.

Rin's whimpers were muffled desperately against the sweat-dampened curve of Shirou's broad shoulder as she bit down hard, her teeth sinking into his skin with abandon born of overwhelming sensation—a sharp, grounding counterpoint to the dizzying spiral of pleasure threatening to tear her apart entirely.

The sudden sting of her own bite mingled deliciously with the deep, throbbing heat coiling tight and insistent low in her belly, each sensation amplifying and feeding into the other until she could scarcely tell where the edge of pain ended and the overwhelming waves of pleasure began. Everything blurred together into white-hot intensity.

She could feel every single punishing thrust with crystal clarity despite her scattered thoughts, every deliberate withdrawal that left her feeling hollow and bereft before he filled her completely again in the next heartbeat, sending fresh jolts of white-hot pleasure radiating outward from her core like shockwaves.

The stretch was exquisite in its intensity, utterly overwhelming—she would swear on her family's name that she could feel every single centimetre of him, could map the exact shape and size, the way he bottomed out completely inside her with each powerful movement, the blunt head of his cock pressing insistently against sensitive places deep inside that made her vision blur and white out at the edges.

Her moans—broken, gasping, incoherent things that barely sounded human—blurred together with her increasingly desperate attempts to simply draw breath, each sound wrenched from her throat without any conscious thought or control.

The obscenely wet slap of sweat-slicked skin meeting skin filled the charged air between them with lewd rhythm, underscored by the ragged, harsh hitch of Shirou's breathing near her ear, hot against her neck. He didn't slow his pace, didn't relent or offer mercy, systematically driving orgasm after violent, shuddering orgasm from her oversensitive body until she was absolutely certain she would dissolve entirely into nothing but pure sensation, cease to exist as anything beyond pleasure itself.

Time lost all coherent meaning in the haze of overwhelming sensation. What felt subjectively like endless hours of unrelenting pleasure—waves of climax cresting and breaking over her again and again until she lost count entirely—couldn't have been more than seven or eight minutes in actual reality. Yet her body thrummed and vibrated with the aftereffects as though she'd been used for hours, every nerve ending still blazing alight, every muscle pulled taut as a bowstring ready to snap.

She felt the telltale pulse and throb of his cock swelling even larger within her already overstretched passage, the way it seemed to grow impossibly further just before— 'oh God' —she felt the first scorching hot spill of his release erupting deep inside her, flooding her womb in thick, liquid pulses that sent another helpless full-body shudder racing through her trembling frame.

Dazed and struggling to focus through the pleasant fog, Rin tilted her head with effort just enough to glance downward between their sweat-slicked bodies. The sight that greeted her punched what little breath remained from her lungs—her swollen nether lips glistening obscenely with mixed fluids, his still-hard cock buried to the very hilt inside her and now painted white with streaks of his thick release. And still, impossibly, he didn't stop moving.

The realisation sent a fresh jolt of something molten and dizzying racing through her pleasure-drunk mind—half shocked disbelief, half delirious anticipation—because of course once wouldn't be remotely enough for him. Not with weeks of pent-up curse-driven need finally being released. Not when he had her like this, utterly pliant and trembling beneath him, her body still clenching weakly around him in fading aftershocks even as he clearly prepared to chase his pleasure all over again.

Shirou, with one final deep thrust that made her gasp weakly, finally pulled out. Rin's body went completely slack against the futon, muscles twitching periodically in residual pleasure as his cock withdrew with an audible wet sound, the shaft glistening under the room's lamplight with their combined fluids coating every inch.

Beat. Beat. Beat.

Now separated, he could now confirm his heart still thundered in the silence.

But he wasn't done—not even close—and with a low, possessive growl rumbling from deep in his chest, Shirou flipped Rin over with surprising ease. His hands gripped her hips firmly, pulling them up and back whilst pressing her shoulders down into the futon. Her shapely rear rose high in the air, positioned just above where her feet were tucked beneath her, position leaving her completely exposed and vulnerable to his hungry gaze.

From this new angle, Shirou could see everything with perfect clarity—her puckered arsehole twitching involuntarily with each gasping breath she took, her swollen pussy absolutely dripping with the mixed juices of both their releases, thick white fluid slowly leaking from her well-used entrance and trailing down the inside of her thighs in obscene rivulets. The sight was utterly debauched, impossibly arousing, and he felt his cock—which had barely softened at all—surge back to full hardness immediately.

He quickly grabbed her hip with one large hand for leverage, steadying her trembling form, whilst using his other hand to grip the base of his shaft and align himself once more with her entrance. The angry, swollen head of his cock traced teasingly along her sensitive slit, dragging up and down through the slick mess they'd made together, gathering their combined fluids as lubricant.

Her back arched beautifully in response to the teasing contact, spine curving in a graceful line, and he could see her cute toes curling tightly from where they peeked out beneath the curve of her raised arse. He could hear her breathy whimpers clearly now—needy, desperate little sounds—whilst her hips shifted restlessly, her body instinctively adjusting its angle to make penetration easier, silently begging him to fill her again despite how thoroughly used she already was.

With this new angle of penetration, Shirou groaned low and deep as he realised with shocked pleasure just how much deeper he could sink into her willing body—each powerful thrust now hitting places inside her that made Rin's breath hitch and catch in ways that neither of them had anticipated during their missionary position. The angle was completely different, allowing him to reach spots that had been inaccessible before, and the revelation sent dark satisfaction coursing through him.

His fingers bit almost bruisingly into the soft flesh of her hips, leaving faint red impressions in her pale skin as he adjusted his grip for better leverage, pulling her back against him with a possessive roughness that sent another visible shudder rippling through her entire trembling frame. The sensation was almost overwhelming in its intensity, and he found himself drinking in every aspect of the moment, cataloguing every minute detail of how she responded to him—every gasp, every clench, every helpless movement.

The thought flickered through his lust-hazed mind as he rolled his pelvis experimentally, testing the new angle carefully before snapping his hips forward again with more deliberate intensity.

Rin let out a choked, desperate moan, her fingers scrambling frantically against the sheets for purchase as she arched her back even further into him, presenting herself more completely. The silken heat of her inner walls clenched instinctively around his invading cock, gripping him like a vice. He could feel her rapid pulse fluttering against his shaft from the inside, could feel the way her body both yielded to his invasion and resisted the overwhelming stretch in perfect contradiction—warm, impossibly wet, and so unbearably perfect that it made his breath catch painfully in his throat.

'She was absolutely perfect.' The realisation struck him with fresh emotional intensity, even as his body continued its relentless physical rhythm without pause.

Then, with a deep growl rumbling from somewhere primal in his chest—a sound born equally of possession and desperate need—he pushed her upper body down with deliberate, commanding force. Her chest pressed flush against the futon beneath them, the soft cotton absorbing the feverish warmth radiating from her sweat-slicked skin as he repositioned her with precise, almost clinical movements despite the lust clouding his mind.

He manoeuvred her pliant body into one of those basic yoga stretches she'd mentioned once in passing—child's pose modified for penetration, he thought distantly. Her arms stretched out before her, bracketing either side of her head whilst her hips remained elevated high in the air, arse presented. The position forced her spine into a deep arch, her breasts flattened against the futon whilst her pussy remained perfectly accessible, spread and exposed. Her breathing had already shifted noticeably into something shorter, shallower, more anticipatory as she adjusted to the vulnerable arrangement.

The thought flickered through his lust dazed mind that he was filing away every minute detail with almost obsessive care—the slight tremor running through her limbs as she settled fully into the submissive position, the way her slender fingers curled reflexively into the rumpled fabric beneath her palms seeking anchor, the soft exhale that escaped her parted lips when she consciously surrendered control and fully accepted the arrangement he'd put her in.

He catalogued with dark satisfaction how readily she responded to even his unspoken directions, how her body seemed to instinctively anticipate his next move before he'd even committed to the action himself, reading his intent through touch alone.

The implicit trust in the way she offered herself up so completely—vulnerable, exposed, defenceless—sent another powerful surge of possessive intensity racing through his veins. He paused for just a moment despite the urgent demands of his body, simply appreciating the absolutely breathtaking sight laid out before him like an offering.

More rhythmic clapping filled the room steadily, the wet, utterly obscene percussion of flesh meeting flesh that would have mortified and embarrassed him deeply under any other circumstances. But here, now, with her trembling and writhing beneath him in obvious pleasure, it only spurred him on further, drove him to move faster and harder.

Her ragged little gasps and broken moans were all that he could hear clearly with every powerful surge of his hips, everything else fading into meaningless background noise.

He wondered distantly if the lewd sounds carried beyond these walls to where Sakura sat, and found he didn't care nearly as much as he probably should have.

From this elevated angle, Shirou could see absolutely everything with perfect clarity—the way her back flexed and her muscles rippled beneath sweat-slicked skin as she tried valiantly to push back and meet him stroke for stroke despite her exhaustion, the faint sheen of perspiration along her elegant spine catching and reflecting, catching the ceiling light, the way her normally neat hair now clung in completely dishevelled, damp tendrils to her neck and shoulders.

And fuck, the sight alone was more than enough to make him push even harder, burying himself to the absolute hilt with each brutal stroke, watching with dark fascination as her entire body rippled and shook with the sheer force of his thrusts. He was utterly drunk on her, on this moment, on the way she responded so perfectly to every single movement he made.

Rin's breath came in broken, stuttering hitches, her moans muffled desperately into the sheets beneath her as she fought with diminishing success to contain the embarrassingly loud sounds threatening to spill uncontrollably from her throat. Each muscle in her trembling body was straining to its limit as the relentless friction burned through her core with exquisite intensity—a sensation that bordered dangerously on unbearable, toeing the line between pleasure and genuine pain.

'More.' The unspoken word echoed between them like a mantra—a desperate prayer neither could quite voice aloud through their breathless panting, though he could feel the sentiment clearly in the way her body responded so eagerly to him, in the involuntary clenching and fluttering of her inner muscles around his shaft, in the way she pushed her hips back insistently to meet him halfway despite her obvious exhaustion.

Shirou grabbed both of her wrists suddenly, his grip firm and uncompromising as he adjusted his stance for better leverage, driving into her willing body with renewed force that bordered on genuinely feverish intensity. He pulled her arms back behind her, using them like reins to control her movements, and the position forced her upper body to lift partially off the futon.

Her body now hung suspended at almost a forty-five-degree angle from the completely drenched futon beneath them—the fabric thoroughly soaked and stained with both their bodily fluids, undeniable evidence of their unrelenting mutual need for one another.

The dramatically new angle allowed him even deeper penetration—if such a thing was even physically possible at this point—and he couldn't suppress the guttural groan of pleasure that escaped him at the sensation of reaching new depths inside her. The change in position shifted everything, altered the angle of friction, and he could feel her responding immediately with a fresh series of trembling contractions.

From this elevated vantage point, he could see her modest breasts swaying and bouncing to the side with each powerful thrust he delivered, the movement hypnotic and mesmerising in its rhythmic quality, and the visual only intensified the fierce possessiveness coiling hot and tight through his chest. Because she could take everything he gave her—because she genuinely wanted it, actively craved it even, had been craving this exact release all along, despite never saying so. And if the way her body continued to clench and pulse desperately around his cock was any indication, neither of them would be stopping this marathon session anytime soon.

Neither of them noticed—lost as they were in each other, in the relentless rhythm of their joining—that in the corner of the room, Sakura had long since abandoned any pretence of listening to music or browsing the internet. The headphones hung loosely around her nape now, forgotten, whilst the laptop screen had gone dark from inactivity.

Her violet eyes were fixed unblinkingly on the scene unfolding before her, pupils blown wide with arousal as she watched her sister being thoroughly taken by the man they both loved. One hand had slipped between her own thighs, fingers working steadily at her core, chasing her own desperate high whilst she committed every detail to memory—every gasp, every thrust, every trembling surrender.

The agreement had been that she would wait her turn, that this first time belonged to Rin alone. But nothing had been said about watching, about bearing witness to their passion, about finding her own pleasure in the intoxicating tableau they presented.

Her free hand pressed against her mouth, muffling the soft whimpers threatening to escape as her fingers moved faster, matching the rhythm of Shirou's hips. Soon, she promised herself breathlessly. Soon it would be her turn.

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END

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