Fate Stay/Night - Medusa & Sakura Matou x Reader

Summary: A mana transfer. An exchange of sperm. Sex. Sakura and her Rider-class Servant, Medusa, were in a terrible predicament after months of unreliable mana. They needed a fresh batch of mana from an outside source—the virile sperm of two healthy young men: Shirou Emiya and you.

It was a ravishing session. You fucked them, you creampied them, you showed them the wonders of a real mana transfer. Shirou Emiya...not so much.

Themes: Reader, Foursome, NTR, Cuckold, Size Comparisons, SPH

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You and Shirou Emiya exchanged glances. To think the two of you would be in such a predicament.

Rider – true name Medusa – was in desperate need of mana. Months ago, during the Holy Grail War, her spirit core was partially damaged due to Caster. Although Sakura could provide her with a great level of mana, Rider was essentially blocked from functioning at full capacity. Sakura Matou needed to reboot her. She needed an explosive source of mana, an injection that would heal her Spirit Core. There was only one solution: mana transfer via sperm from two strong, healthy, and potent males. The lucky men chosen for this task were you and Shirou Emiya.

Filling Sakura Matou and Rider Medusa with cum was a dream come true. Nobody could deny their allure, especially as a duo. There was sweet, innocent Sakura with her large, bountiful mounds and child-bearing hips. Her doe eyes and her devotion to her seniors made her the epitome of the male fantasy. Yet nearly everyone, from her admirers to her worst enemies, suspected she was different in bed. Quiet and kind on the outside but freaky in the sheets.

Pair the shy, passionate woman with Rider Medusa, the minx of Greece, and the situation became ten times better. Medusa's long, supernatural purple hair and her tall, slender physique was the envy and admiration of hundreds. She was a Heroic Spirit from the past, so of course she was flawless. Although naturally an introvert, the woman in glasses could seamlessly switch to a seductive persona worthy of the Gorgon name. With Sakura as her master, it was a match in heaven. Sakura becoming less and less ashamed as her Servant encouraged her to explore the branches of her sexuality.

Regardless of the ups and downs, the task was going to be tough. To supply them with enough mana to reaffirm their bond and click Rider's Spirit Core into place was easier said than done. Medusa was a supernatural entity with incredible stamina ands strength while Sakura was a natural slut with an insanely high libido.

In anticipation for the mana transfer, you hadn't masturbated for a month. Your balls were full and aching. Judging by Shirou's trembling lips, he did the same. Neither of you could wait.

Sexy. That was the sole word describing Medusa, the Rider-class Servant. Shirou might not have wanted to admit it out loud but she was. Every other Servant in the Holy Grail were second to her in the seduction department. She could be an Assassin-class Servant with how alluring she could be. A master, man or woman, enemy or ally, could fall into her willowy traps.

Both her and Sakura were stark naked. The pink bed appeared hazy, almost angelic as the Master-Servant paired looked back eagerly. Medusa's long, creamy legs and narrow, tempting eyes; Sakura's DD-cup breasts and cute, endearing pupils...

Despite the supposed difficulty of the arrangement, neither of you complained or second guessed yourselves. You wanted this and you were going to do it.

Rider licked her lips and announced, "Let's begin, boys."

While Shirou stuck with Sakura, his girlfriend, you were tasked with Rider. Honestly, you would have it no other way. Sure, Sakura had bigger tits but Rider possessed an aura of maturity and lewd flirtiness her young Master didn't.

You and Shirou stood shoulder-to-shoulder at the edge of the bed. The ladies crawled over and unzipped your respective pants. A mana transfer this might have been, it was also a foursome. Everybody wanted to have a good time.

Your pants flew down with your boxers quickly following. Rider's expression went wide in surprise.

"Oh…"

"Senpai…"

Hearing Sakura's tepid voice, you glanced over to your right. Sakura was hot as always but…

"Heh."

Shirou was…well, it was hard not to laugh. Flaccid, he was tiny. A worm nestled on a measly ballsack. Sakura's hands flew to her mouth. You couldn't tell if she was muffling a squeal or a giggle.

"S-sorry," Shirou said, scratching the back of his head. "Nerves, y-you know?"

You certainly understood. Being naked with another guy was awkward and new for you. Despite the hot babes in front, neither of you were hard.

"I…I think it's cute, senpai…" Sakura said through her cupped hand. Her eyes were glued to the underdeveloped manhood. Her crush, her love, her obsession–she imprinted his itty-bitty softie in her core memories.

Rider, so far, hadn't said a word. She, like Sakura, was laser-focused but unlike her Master whose emotions were difficult to decipher, it was easy to see what she thought.

Eyes wide, lips parted, she was shocked. A couple light exhales later and she spoke. "I see someone has been hiding a snake…"

You swallowed. The tone in which she said those words–it was intoxicating and low and needy. Rider's sultry remark brought Sakura's attention to your flaccid dong. She blinked twice, genuinely amazed.

"A-amazing, it's so long," Sakura said before she could stop herself. "N-not that there's anything wrong with yours, Senpai. Um…"

"It's alright, Sakura–" Shirou's voice dropped as soon as he glanced at you. His throat made an undignified sound. "W-woah. Wow."

All this attention made you clam up. Nevertheless, it appeared nobody could believe your size, even Shirou.

Actually, especially Shirou. You could see his eyes and mouth trembling in astonishment.

You took another look at Shirou's manhood. Somehow, it was smaller than when you first glanced at it, if that were even possible. You estimated he was below an inch and as thin as a pinkie finger. Moreover, the pebbles serving as his family jewels were contained in a tight, wrinkled pouch. Everything about it seemed to be miniature. You briefly wondered if he suffered from having a micro penis.

Judging by the way he straightened up, the possibility was certainly there.

"Senpai, look at me please," Sakura called out. The poor boy had been so preoccupied by insecurity he didn't notice Sakura begging for his attention. Upon seeing her glorious figure from above, Shirou Emiya gulped.

"Do you want me?" Sakura asked.

He nodded, forming a smile.

Without warning him, she picked his limp cock up and gently began pumping it with two fingers. A low hum came from Shirou as he got hard.

There…wasn't much to gain.

"Is…is this it?" Sakura asked, tilting her head.

"Yes…" Shirou muttered. "You're doing great."

That's…not what she's asking, you said to yourself, pursing your lips.

Sakura wasn't questioning if she was doing a good job. She was asking if this was it – if this was her lover's full, erect size. Out of not wanting to embarrass the poorly endowed redhead, you chose to remain silent. Sakura did the same.

Less than three inches, Shirou's cock throbbed. Tiny little veins were riddled all over it, almost abnormally so. It twitched and jerked and pulsated, like some sort of monster. The rational explanation was that it was sensitive. You sincerely hoped Shirou wasn't a premature ejaculator. From one man to the next, he already had so little going for him. A small dick and a quickshot? Even the worst men didn't deserve such curses.

The expression on Shirou's face was tense. Almost fearfully, his eyes darted at your flaccid dong, and said fears came to pass.

At his hardest, Shirou Emiya was still smaller than you. It would have been hilarious if it wasn't so pathetic.

Your balls dangled much, much lower than his, and seemed to be packed with more sperm than Shirou could emit in a lifetime. Despite the fact you were both men, when it came to the part of yourselves that enforced your manhood, there was no competition. No room for debate. You were better. Bigger.

And this was while you were soft.

Sakura looked between you and Shirou, clearly disappointed. The love of her life didn't live up to her lofty expectations.

A cold hand enveloped you. You glanced down, relieved. Finally, Rider was making her move. It took her a while to break out of her stupor. A sultry smirk on her face, she worked her cock, granting it a few seconds to fatten up, before swallowing.

Immediately, you found yourself groaning. Her tongue was immaculate and targeted the underside of your head – your most sensitive area. A rush of blood went down your nether regions and your cock reached its full size in a matter of seconds. Rider didn't anticipate your growth and your newfound length hit the back of her throat. She gagged and choked and eventually relented.

"Phaa….!" Your cock slipped out after a few tugs, her spittle having drenched it. It glistened and throbbed powerfully. She gave a polite kiss to the tip.

"I-it's so big," came the stammering Sakura. "So much bigger than yours, Senpai."

Disillusioned by the glossy and superior phallus, Shirou replied as if hypnotized, "Yeah, it sure is…" Those were true feelings. His innermost thoughts that could only surface when realizing the truth of defeat. A situation where he instinctively and rationally knew he could not hope to win.

Yet his male pride kicked in anyway, the last firewall to prevent him from getting cucked.

"B-but I can get harder, Sakura! See!?"

"Really?" Sakura brightened, stupidly believing him. With an affirming smile, Shirou jerked himself off.

One minute, two minutes passed.

Sakura's expression turned to disappointment again. She awkwardly watched her crush try to be something he wasn't – something he could never be. His cock did its best to break its limits but ultimately it amounted to nothing.

You dwarfed him as though he was a child. It was a miracle the two of you possessed the same organ. The difference was that baffling.

While Shirou was busy disgracing himself, you were getting your dick sucked by Rider. The small drips of mana – your pre-cum – served her well. You could feel her getting stronger by the second as she took in your heat and sweat.

Her tongue was long, like a snake. And with it, she was able to wrap herself around your girth whilst sucking with the force of a high-ranked Noble Phantasm. Your legs began to shake, your cock feeling wet and warm and loved.

Rider was fucking amazing.

She would retreat sometimes, expose your cock to the open air and tease it with her tongue. She would swallow again and suck you off. She fondled your balls and made sure each orb was massaged properly. And most importantly, she maintained eye contact. Her pink glasses were nearly on the verge of falling but neither of you cared. Not when you were getting close.

You placed a hand on her head. As a Servant, you knew she could take anything you threw at her and then some. Therefore, you saw no issue in grabbing her and forcing your entire cock inside her throat.

Her nose poked your pelvis.

Her eyes narrowed in concentration.

You repeatedly dragged her head up and down your length. There was no mercy or control behind your movements. You simply wanted her to serve you – to be your Servant, your personal cock-obsessed whore.

Like last time, she gagged. But Rider must have been a quick learner because she made significantly less noise this time around. More deepthroating. More focus. Tighter.

"I'm almost there…"

As you groaned, the expected pressure of a climax arrived, pulsing and thrilling.

"Rider." Your voice cracked, uncharacteristically weak. Another groan followed. This sensation, her tongue, her mouth, it was too much. This was no ordinary deepthroat. Perhaps it should be expected of a Servant but it was out of this world. Something you could only describe as though it were a myth. The sensations of delight and arousal were a thousand times stronger. Your cock felt like it was on fire as it came closer and closer to release.

The weight of your cock in her mouth, Rider still managed to form a bold smirk. Her lithe hands tugged at your balls, urging them to unleash their contents.

You bit your lip. Rather than announce your orgasm, you decided to keep quiet and surprise her. Yet the way your cock throbbed madly in her throat, there was no way she didn't know.

"Gah!"

Rider sucked you off with force no human on this Earth could imitate. She was vigorous and thorough and above all erotic. Her hands squeezed your balls. She was literally draining you for all you were worth. Every last drop and very last speck of sperm. She wanted nothing left. She wanted you empty.

You came like you never had before. A massive, body-bending orgasm, spewing heaps and heaps of cum.

Rider gulped it down. All of it.

Your seed might as well have been forcibly taken from you.

It took a while for you to stop. It felt like you were letting out a tsunami. An endless torrent of your essence going directly inside the tall, voluptuous woman.

Although Rider was as thorough as could be, a line of your seed still oozed out from the corner of her mouth.

Like some cum-addicted slut, she licked it up and opened her mouth.

Swallowing thickly, your cum disappearing in the next instant, a smirk settled on her devious, sexy face.

"So much mana. Such thick mana." Her voice was low, husky, and seductive. "And it seems you're ready for more, mm?"

Rider's little show prevented you from softening in the slightest. In fact, you got harder. Your balls, which had been clenching tightly, were now in a state of relaxation as they generated excess sperm.

"Agh…" Shirou was reeling from Sakura's own blowjob. He was semi-erect, struggling to maintain his strength. You heard the little grunts and moans, and it appeared Shirou came after about a minute.

Unlike you who enjoyed a good six minutes inside the skilled, tantalizing mouth of Medusa, Shirou was unable to last a minute under Sakura's inexperienced and sloppy blowjob. And to top it all off, in the five minutes between your climax and his, Sakura had been desperately trying to revitalize his cock. Sucking and nibbling and grabbing at his meager balls, to no avail.

"Senpai, please…" Her eyes were watering. "Am I not pretty?"

"You are, Sakura! You are! I just…" You could tell Shirou was cursing himself in his head. His refractory period was hitting him hard. "...nerves! Sorry!"

"B-but look at him!"

Their eyes went towards your long, throbbing member. It was larger than before. Stronger and more rigid. Feeling their gazes, you exhaled and felt yourself grow ever so slightly more.

Shirou blinked and looked down at himself. Frowning, he jacked himself off as fast as he could. His limp didn't respond–

"Over here."

–not until Rider spoke and grabbed everyone's attention. Shirou's dick skyrocketed.

Her ass sticking out, her gaze slightly turned, her sensual charms turned up to the max. Sakura, noticing her senpai's change of heart, quickly did the same. Crawling forward and pushing her thick rump invitingly.

"Senpai…" Sakura called out, provoking the redhead. "I need you…I'm so lonely."

You and Shirou gulped. Sharing a look, you absorbed in your respective cocks and their sizes and abilities.

"Think you can handle it?" Shirou asked.

You eyed his tiny cock, raising a brow and gesturing to Sakura's dump truck of an ass. No words were needed. Shirou flushed, ashamed.

"H-hey, don't underestimate me." Shirou huffed and got on the bed. Shuffling on the bed and lining himself up, it gave perspective into just how small he was. You wondered if he had enough inches to penetrate the mounds of cheeks and reach her pussy. Honestly, with the way Shirou was holding his shaft, he seemed to think the same. He doubted his ability to fuck her.

You didn't. You confidently went behind Rider and copped a feel of her booty. She smirked, allowing your fingers to massage her toned ass.

You and Shirou decided to plunge into their wet cunts in the same moment.

Yet the reactions were totally different.

Rider moaned and gripped a heapful of the mattress. Her back curling and her expression stunned and happy and restrained.

Sakura looked on with envy. She glanced back at Shirou and said, much to Shirou's shock, "A-are you inside, Senpai?"

He was already inside yet…Sakura barely felt it. He decided to pull back and slam into her with everything he had. There was a spark of pleasure and Sakura mewled. The reverberating clap told her what she needed to know.

"We're together, we're connected, Senpai~"

"Yeah," Shirou said, smiling. "We're together."

Their precious moment was deftly interrupted by the sound of you clapping Rider's cheek. Holding her tightly, you made sure to hit her most sensitive points.

"Ah! Ah! Mmh! Ahh!" Rider's spine arched. Moans erupted from her like a volcano. The noises were obscene and almost fake, but there was a level of spirit in it that simply couldn't be faked. She wanted it. She wanted more. "That's it! Faster! Deeper!"

With the way you were carving out her pussy, it was only a matter of time before you started plowing her G-spot.

Her walls suddenly wrapped around you tightly. "I'm there!"

Her fluids dripped from her overstuffed snatch, utterly aroused and having reached a primal climax. She arched her back long enough for you to grab her hair and reel her in, plunging her cock even deeper.

"Aaah~!"

The loud moans coming from Rider made Shirou self-conscious.

"Sooo good!"

Shirou winced. Sakura wasn't making sounds remotely as audible or elated. She was grunting and smacking her hips against him and smiling. Yet nothing told him he was actually fucking her. Where were the moans? The orgasms?

Shirou picked up the pace. The two of you were perfectly in sync, each clap echoing at the same time. Shirou thought by matching your pace he could satisfy Sakura.

"Oh, Senpai…" Sakura smiled that sad smile of hers. Shirou didn't understand. He was the same as you. He was clapping cheeks the same as you.

What was wrong?

He got his answer in the form of you drawing out the length of your cock. You were big. Much, much bigger than Shirou. With his little dick, Shirou should have been able to enter and exit Sakura much faster than you. But he didn't. He couldn't. You were better, plain and simple.

The realization preemptively made Shirou go over the edge. "S-Sakura!" he cried out, dumping his load inside her.

"Inside, Senpai! In my womb!"

Whether Shirou could actually accomplish such a thing was hard to say. Even Shirou wasn't confident but he shot his load anyway. Three, six, eight thin strings of cum.

His cock wilted faster than a faded flower. Before he fully pulled out, he was drained and exhausted.

"Senpai, you're not done, are you?"

Sakura's question was overshadowed by the next door sounds. You were railing Rider like a train and the couple witnessed the event in disbelief. Hugging like the pillow was her life line, her sole anchor to this world as she achieved climax after climax. Toe-curling orgasm after toe-curling orgasm.

Sakura's jaw dropped. Shirou's cock twitched.

Soon, the time arrived. You pushed yourself inside her to the fullest, balls slapping once, and came.

"Auh~!"

Rider's moan was accompanied with a sharp groan from you. You were cumming buckets, your balls squeezing themselves dry.

By the time you pulled out, Rider was in a half-delirious state. Eyes struggling to stay open, face buried in her pillow, body shaking and trembling. Filled to the brink and beyond, creamy volumes of cum fell out of her demolished snatch.

Shirou's cum, to compare, was still inside Sakura. Unable to move, significantly less thick, and most of all a fraction of your volume....