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Every day you thanked the gods and your own wisdom, because you were never quite certain which one drove you to stay your father’s hand. It was a spur-of-the-moment decision based on nothing but gut intuition; a simple word emerging from you as the young lord, Muzan, raised the blue spider lily medicine to his lips.
“Stop.”
You had never forgotten your father’s incredulous stare, nor the way Muzan’s accusatory carmine gaze fell upon you, silently demanding an explanation for your outburst. Yet he lowered the cup to his lap untouched the moment you spoke. He trusted you, and thank the gods for that.
And the image of the ox you fed the formula to instead, demonstrating your hypothesis that the medicine was dangerous, was one burned deep into your memory. The frantic beast charging, eyes blood red and seemingly intent on wiping every living being from the face of the earth before perishing in the sunlight. It haunted you. The possibility that Muzan could have suffered a similar transformation, that he could have been transformed into a monster, a yokai, didn’t bear thinking about.
Had your father spawned any child but you, he would have been executed.
Five years passed and you were the only person Muzan entrusted with his care. He was a wretched, foul-tempered, petulant man– a man you were the sole physician to, and the man you adored.
As you watched the nobleman and his entourage ride down the road toward his estate, resplendent in their finery after a month spent at court, you felt an overwhelming pride. Not just that his improved health was a testament to your skills as a doctor, but also that he was undoubtedly yours.
Muzan had never fully recovered from his ailment, and likely never would, but under your care he had grown stronger; strong enough to attend his duties as a nobleman and landowner. And strong enough to be a persistent yet welcome nuisance in your life for the five precious years that had passed since the day you met him.
You couldn’t help but smile as his horse broke off from the rest of the group to ride ahead toward you, the rest of the men veering off to their own families.
“I had a feeling there would be a bad omen waiting on my doorstep,” Muzan grumbled as he drew closer to you, stopping his panting horse so close to you that you could feel the heat radiating from the beast. “The sun rose scarlet and I knew there would be nothing but torment awaiting me.”
“Yes, I saw a similar omen this morning too,” you countered. “My tea leaves warned me of a malicious presence riding in from the south. Had I known it would be quite so disagreeable I would have boarded the windows.”
“I’d have ridden slower if I’d known you were waiting for me.” The faintest hint of a smile curved Muzan’s lips as he slowly and carefully dismounted his steed, pulling his walking cane from the saddle and leaning on it as he made his way over to you on stiff, aching legs.
“Ah, my apologies, my lord. Are you not the same Muzan who wrote to me every day begging me to be here upon his return?”
“You’re mistaken.”
“Curious. I could have swore the letters currently spilling out of my drawers were from a pitiful nobleman named Muzan who longed to feel the warmth of my embrace and taste the sweet nectar of my cun–”
“Oh silence, damnable torturess of mine, you've had your fun.” He gave you a withering glare, offering his arm to take you into the house.
“Far from it. You've been gone a long month. I have a lot of fun to work out of my system.”
Muzan chuckled monosyllabically as you took his arm, squeezing it tightly between the crook of his elbow and his side. His affection was always subtle, but through the years you had learned to appreciate it. It was rarely delivered in grandiose declarations– not unless he was out of his mind with pleasure anyhow– but it was there if you knew where to look. A brush of his hand against your back, the barely perceptive softening of his perpetual frown, that he had turned down multiple marriage offers from ladies of equally noble houses to his own, and that his reluctant smiles came all too easily when he was with you.
Muzan owned the land you lived on, but you most certainly owned his heart. And, as he frequently insisted, you owned every other part of him too.
A while later Muzan sat in the steaming water of the onsen a short walk from his estate. The water was low enough that even while sitting it only came halfway up his chest. His body had changed, albeit subtly, since your first meeting. Your treatment and his resilience had allowed him to gain muscle, and though he was still somewhat slender, he was undoubtedly altogether fuller. His complexion which was once so pallid, was healthier and flushed with vigor.
Muzan huffed in protest, furrowing his brow as you busied yourself with his medicine. “You know, the other nobles at court don’t bathe. They reek of perfume but it doesn’t quite disguise the smell of their bodies. It’s stifling.”
“Well, it may be unfashionable, but as your doctor, I insist you bathe. And as your mistress, I demand it.”
“You misunderstand. I’m not complaining about bathing. I have no wish to spend a second longer than necessary stinking of horse and other people. I’m complaining because you’re taking too long with your damned elixirs and my cock aches.”
“You’ll have more to complain about than an achy cock without your medicine. Be patient.”
Deep down you knew his carping was all in good humor. You knew the man outside and in, afforded the duality of insight which only a doctor and a lover could have. And he knew you would take his grumbling in the spirit he intended.
Muzan chuckled dryly as you approached with a bowl containing a deep red liquid, balancing at the water's edge to offer it to him. “And what is that little concoction, mistress of mine? Are you attempting to murder me like your father before you?”
You simply met his gaze with your own unimpressed one. He knew as well as you did that there was no malicious intent behind your father’s mistake. Muzan’s humor was as dark as his rotten little heart, and you adored it just as much.
“Yes, indeed I am. I’ve merely kept you alive these past five years to extend your torment. And for my own pleasure, of course,” you teased flatly. Reaching around to wrap the jet black silk of his hair around your fist, you firmly yet slowly pulled his hair back leaving him no choice but to raise his face, his lips meeting the rim of the bowl as you gazed into his eyes. “It’s your usual medicine, except now the wineberries are in season and I thought they might make it more palatable, hence the color.”
Dutifully, he parted his lips and sipped from the rim, his eyes fixed on yours, filled with longing and desire.
Though he would never speak the words, you knew he had missed you dearly. You knew because you had pined for him just the same and your souls were irrevocably intertwined. Whether he lived for another year, or five, or fifty, you would find him, know him, and love him in every life, of that you were certain.
When the remedy was gone but for a blood-red smear across the porcelain, you set the bowl aside and leaned down, kissing the scarlet stains from his lips. The sweet tang of berries accompanied the fervent hunger of his kiss as his arms wound around you, slender but strong, and soaking your clothes with onsen water.
“Bathe with me,” he begged, pressing his brow to yours.
“Let me undress–”
“No time.”
Your stomach flipped as he pulled you into the water on top of him, clothes and all, ever petulant and demanding. But the fact he had strength to pull you into the pool was a miracle of both your making and his, and so you could never truly resent him for it. Not really.
“Damn it all, Muzan Kibutsuji,” you scolded him half-heartedly as you planted your knees on the stones at either side of his thighs, straddling his hips. “My clothes are ruined.”
“Then consider me jealous of them,” he said, the heat of his breath fanning over your lips as he moved in as if to kiss you. But as spoiled and insistent as he was, he knew better than to cross that line. His lips were yours to claim, not the other way around. And he would wait, though his temper would grow fouler by the minute if you didn’t give in to your shared desires.
“Is that an invitation?” you asked.
“A plea.”
“To be ruined?”
“Yes,” he said, the word little more than a heavy breath heating the air between you. “Gods, it’s been so long. I need...” He trailed off, pressing his brow to yours as though he was embarrassed to put it into words.
“Use your words, my lord…”
Closing his eyes, he filled his lungs and summoned his resolve. “I could recite every word of my letters to you and it wouldn't be enough to convey my hunger. Fuck me,” he said, and then after a moment’s pause, “please.”
Any other day you’d make him grovel, drag out his torment until he was begging for the taste of your cunt, but in truth you needed him urgently.
The onsen was by no means reserved only for him, but the likelihood of someone passing by was slim. Still, it wasn't wise to delay. Bundling the soaked swathes of your skirt, you shifted your hips until the fat head of his cock pressed insistently against your entrance, his eyes pleading with you to end his torment and begin his ruin.
Lips only you knew tenderness from parted around a gasp of desperation as he fought the urge to thrust up into you, knowing it would only lead to disciplining. And while he did sometimes enjoy punishments– albeit with a fair amount of cursing– his desire outweighed even his most petulant instincts.
Still, you let your lips hover close enough to his that ghosting touches sent shivers through both of you. The skin on his chest and shoulders pebbled and his breaths fractured. The corners of his lips curved into a smile so subtle you might have missed it, had the shape of his mouth not been one of the many details of him which had distracted you for the past half decade.
And the moment you gave in to your urges, kissing him as you had craved for that long and lonely month, he moaned against your lips, his thighs twitching beneath you, desire making his cock throb against your cunt. So eager for you; the noble lord simultaneously powerful and helpless, awful and wonderful. And yours without question.
His back arched, exposing his throat as you finally lowered yourself, sinking down onto the thick length of his cock. The space between his eyebrows puckered as he emitted a low groan of relief and pleasure, the fingers of one hand digging into the plush of your ass, the other braced against the onsen floor behind him.
He sucked his breath between his teeth as you rode him, aching muscles completely forgotten. Water sloshed and churned with the rhythm of your thrusts, trickling down his chest, soaking you through. Nothing you had imagined during his absence could compare to the comfort of having him there. Though you had never left, it felt as though you had both come home.
Muzan was yours, surrendering to you and you alone. You cherished the warmth of his throat beneath your lips as you lapped at the little valley between his clavicles. His groans rumbled against your tongue, causing your lips to curve.
“I missed you,” he gasped, eyes squeezed shut. “Every damn day I was away from you.”
“Did you dream of me?” you asked, enduring the ache in your thighs.
“Yes…”
You leaned in closer, pulling his head toward you, whispering against the shell of his ear. “Did you stroke your cock imagining this?”
“Oh fuck— yes.” He clenched his teeth together, barely holding on to his composure as you teased the tender bud of his nipple with your fingernails. “Oh! Oh Gods… oh fuck… more… please… mmh— oh gods, you’re mine… mine… I belong... to you.”
His eyes rolled back, teeth pressed against his lower lip, thighs trembling as he came.
“That’s it,” you whispered against his ear. “Cum for me, Muzan. Give me what’s mine.”
“All of it. All of me. Ohhh fuck fuck fuck thank you, I’m yours.” He exhaled heavily, breath shaking from the intensity of his release, lips seeking yours as his hands cupped your face, leaving droplets of water along your jaw. “I’m yours,” he said again, resting his forehead against your chin, fighting to regain control of his breath. “Fuck, I adore you.”
And he did, of that you had no doubt, no matter how often he insisted you were a plague besieging his home, or that your medicine was the most bitter he’d tasted. There was no doubt that however many years he had remaining, every one of them would be spent with you.