Yuna's Hands-on Lessons on Anatomy

You both start when your bedroom door suddenly opens, and your mother's head pokes through the narrow gap, her facial expression unreadable as she drinks in the sight of her beloved son sitting next to such a beauty. Said beauty was demurely dressed, and though seated mere inches away from you, betrayed not a hint of tension nor desire; yet your mother's eyes crinkle at the corners nonetheless as she analyzes the girl in ways unbeknownst to the lesser senses of men. Apparently satisfied, she nods at both of you, before dryly announcing, "Your father will be somewhat late tonight, so I'm heading out to do some errands. I should be gone for a few hours..." she seems to linger on those last words, the faintest hint of a smug grin stretching her lips before she disappears once more, leaving with a bland, "Have fun!" as she stomps down the stairs and out the front door. Leaving you entirely alone in the house with the gorgeous Yuna, who innocently indicates the unfinished presentation on the reproductive system you both were currently working on,

"Let's continue then! I'm sure we can get so much done before your parents get home..."

The previous afternoon you had brought Yuna home for the first time, and your mother's eyebrows had quirked in surprise, while your father's had danced a merry polka across his forehead. Naturally they had been shocked their modest son had bagged such a catch, though their enthusiasm had dampened only somewhat when you blushingly informed them that she was just there to work on a project with you for anatomy class. Your dad had suffered from a minute-long coughing fit after that, and your mom's welcoming smile had grown glacial as her non-verbal interrogation of the hussy accompanying her dear child intensified. Evidently Yuna had passed whatever torturous enquiry your mother subjected her to since she was allowed inside of the house, and was given the slow nod of one predator greeting another at the watering hole. Yuna had even been allowed to join you in your room, where you had studiously worked on the presentation, even with your mom wandering in from time to time to offer snacks or drinks; your dad's continuous cackling went unmentioned. Your fellow student had left without incidence, and with the work only halfway finished, you awkwardly informed your parents that she would be returning the next day to help complete it. Your mother's face had been serene while she bobbed her head in acquiescence, and you could have sharpened steel on your father's grin.

When you had returned home today, with Yuna in tow once more, you had been surprised to find that your mother was the only one home, and was wearing her makeup. You had felt Yuna stiffen at the sight of your mother in her war paint, while your mom's gaze swept over every inch of the girl's body, drinking in her modest yet showy outfit, her modest makeup, her appreciable curves, her bashful demeanor. Your mother's eye had twitched, before she welcomed you two in with a cheery smile, and had surprisingly left you both alone to attempt to figure out the least mortifying way to explain sex to your class. After barely half an hour your mom had stuck her head in, told you she was going out, and left you alone with one of the hottest girls in school...

So now there you were, with Shin Yuna mere inches away from you, her curvaceous body distracting you immensely as you struggled to pay attention to the... content of the material. Smart, gorgeous, somewhat bratty, and rumored to be an idol, Yuna had been a favorite of both the teachers and the student body since her arrival. Your lecherous Health teacher had positively leered when he had doled out your topic for the anatomy presentation, and the class had either chortled along or glared at you furiously for your luck in getting picked to partner with her. But so far Yuna had betrayed not an ounce of impropriety, though her every careless touch had set your heart racing, and your pants feeling decidedly too tight. Of course you had tried hard to banish the impure thoughts rushing through your mind, but it was difficult with her hand brushing against yours and her breasts oh so delicately pressing against your arm when she would lean past you. Yuna's innocently pink outfit left little for the imagination as well, and though her most intimate parts were still covered, she still managed to show herself off with a lowcut dress and skirt. You would have thought she was arousing you on purpose, but you were baffled as to why she would show any sort of interest in a normal pleb like you.

After an hour of rigorous if increasingly distracted work clustered around your aged laptop and a heap of textbooks, you had reached an impasse. Yuna sighs in frustration, her luscious lips pouting while she struggles to deal with the problem at hand, namely how best to produce an A+ presentation when you both knew the female half of the class would be bringing their best to the table to try and humble her. She leans close to you, her shoulder sliding against yours as she asks, "So, any ideas?" she waves a hand, "The problem with doing the reproductive system is that it is just so hard to make sound interesting, everyone else will be doing real experiments to show off their parts of the body, but all we have are boring diagrams!" she huffs, "If we got the arms or something we could test how different weights affect the muscle angle, but no," Yuna rolls her eyes, "We got... our bits." Seeking to cheer the gloomy girl up, you awkwardly joke about not having to do any experiments, which makes her eyes narrow. You start to apologize, but she shushes you with a finger, "Shh! I'm thinking..." A surprisingly wicked grin sneaks across her face and is gone before you can even be sure it was even there, as she turns to you and calmly says, "I think we do need to do some experiments..."

"C'mon, take off your pants, we don't have all day you know!" Yuna stares earnestly at you, wiggling her hand at you as if telling you to take your dick out was something girls commonly did during group projects. She puts her hands on her hips and glares at you from her perch on your bed, "How are we supposed to test the statements in this book," she jabs at a textbook detailing in the blandest terms imaginable the act of coitus, "if you don't provide the evidence for the male half of the equation? So, take it out! The project is due tomorrow morning!" You glance around furtively, but under Yuna's intense glare you find your excuses withering on your tongue, surely she knew best, and wasn't as if she wanted to... you know, do it. There had always been rumors, and many of the girls did seem to loathe her unreasonably, but nobody could seriously believe that Yuna could possibly be the school bicycle! So with much trepidation, you drop your pants, and at her further urging, let fall your boxers as well, leaving you with your hands covering your manhood in front of the most gorgeous girl in school. Yuna watches your face turn bright red before noting, "You know, it's hard for me to examine it if your hands are in the way."

"'When aroused,'" Yuna reads, "'the penis becomes engorged, extending to twice or even thrice its flaccid length, and becoming rigid,'" she raises an eyebrow as she pokes at your decidedly undeployed manhood , "So, why is it not hard yet?" She taps at her lips while she ponders the issue, before nodding thoughtfully, "Does your penis require... stimulation? And here I thought boys got hard pretty easily, I noticed you getting a stiffy several times already today!" You sputter out excuses but she silences them with a flick of her pen, "Or, is your member tired because it's been getting up all day?" Yuna hums happily to herself, "There's so much to test for! This project is going to be fun!" Without even bothering to ask permission, she tentatively places her hand on your thigh, watching with interest as your cock twitches from her mere touch, stiffening modestly under her appraisal as your lust eats away at the incontinence caused by your nervousness. "Interesting," Yuna muses, "Describe to me how it feels? We should probably measure it to determine where it lies on the chart for average penis size!" She has a gleam in her eye when she whips out her ruler, and you groan internally, a girl was about to touch your dick for the first time, but she was only doing so for science!

After fifteen minutes of exhaustive and increasingly intimate inspection, Yuna is satisfied with her initial findings, and your poor cock is now firmly erect, "Excellent, I think we have enough information about the male half of the equation, and I can supply the female half on my own. Feel free to put your pants back on," Yuna says absently while she jots down yet more notes, biting her lip while she concentrates. Somewhat disappointed, you hesitantly start to pull your clothes back on when Yuna suddenly stops you, "Wait. We're missing something," she contemplates, "I think... I think we're missing the most important part! We can't just analyze them separately," she looks at you excitedly, "We have to analyze them together! Keep those pants off mister, we still have science to do!" Yuna stands up and reaches under her skirt, before leaning forward to pull down her plain panties, her face only inches away from your manhood. Your heart pounds in your chest as you realize that you are now alone in a room with your cock out, and a girl had just taken her panties off, which could only mean... Yuna hops back onto the edge of your bed and opens her legs, pulling the hem of her skirt up to reveal her nubile pussy, "Now then, let's experiment, shall we?" Yuna asks with relish.

"Hmm," Yuna notates, "the male subject's penis has grown noticeably larger, and the tip is..." she eyes your cock, "now thoroughly engorged with blood, perhaps to aid in penetration?" You continue to stand dutifully in front of Yuna while she jots down her observations, your manhood twitching as you wait only a step away from her font of fertility; your balls aching terribly. She nods in satisfaction, "It would appear that my hypothesis that the presence of an exposed vagina would cause the penis to grow to its maximum extent was correct, now then," Yuna reaches a finger down to probe at her own genitals, running it through her pink folds and pressing at her prominent hood at the top of her slit, "My vulva has become extremely sensitive, and my... oh. Oh my clitoris is... mmmph..." Yuna's eyes roll back as she trembles from her exploration, before regaining control of herself and continuing, "My arousal is also noticeable, and my vagina is..." she shudders as her finger slips inside of herself, "Oh. It is extremely wet..." she removes it, dragging a glistening streamer of grool that she wipes against her bared thigh, "Likely due to the presence of a fully erect and available penis so close to it," Yuna pauses, breathing heavily, her face now as flushed as yours was, "I think... I think we need to proceed with testing... I am... thoroughly aroused," she looks at you plaintively, "and we cannot risk premature ejaculation. Please enter me. Now."

You could not believe it. Yuna, one of queens of the school, was telling you to fuck her, she was begging you to stick your dick inside of her, and she had not even mentioned protection. Your brain was so frazzled by lust you did not even bother to consider the aftereffects of your coitus, you simply stepped between her legs and pushed your cock against her moist slit. Yuna sighs, "Lower, lower, here, let me-" her hand finds your member and guides it to her entrance, so that when you press forward you feel her warmth engulfing your dick. You both groan as you press all the way inside of her, your manhood filling her pussy to the hilt, and you pause there while you both tremble with pleasure. You start to pull back so you might thrust into her once more, but she stops you with a hand on your chest, "Wait... before we continue... describe how I feel... We- we need to record this!" But your hind-brain has no time for such complex thoughts, and your hips unconsciously move on their own, making you both moan once more, "Oh fuck!" Yuna curses, "Your cock... I can't think straight!" Her legs wrap around your waist as she tosses her notebook aside, "Just... just do me, okay? Let's just focus on the sex for now!"

So, you fuck Shin Yuna, just like how she asked you too. Her pussy grips you like a vice while you slide in and out of her, your shaft gleaming with her juices as her cunt slobbers all over you both. And her warmth... you had never realized how warm a girl could be, your cock felt like it was being broiled inside of her and you never wanted it to stop. Yuna seemed similarly afflicted by pleasure, squealing and gasping with every thrust, begging you not to stop as her popular pussy takes every inch of you with euphoric ease. Your balls begin to pulsate, and the thinking portion of your brain battles furiously to take control and shove through the thought that perhaps you should not empty your load ballsdeep into your classmate's fertile pussy; but her legs give you no option of pulling out, "Your cock!" Yuna exclaims with wide eyes, "It's twitching! Are you... oh you are... you're going to inseminate me!" she nods eagerly, "Yes. All in me! Cum in me! Yes! OH FUCK YES!" Yuna shrieks at the top of her lungs as your jizz pours inside of her in an uncontrollable tide, her walls clenching tightly around your length while you spasm atop her, convulsing with pleasure. It feels as if your brain was draining out through your cock, leaving you gurgling while you erratically thrust into her during your orgasm.

It takes at least a minute for you to recover, your nerves shredded with overstimulation as you slowly pull out of Yuna, allowing your conjoined sexual fluids to drip out of her gaping hole. Who looks down in wonder at your slowly softening erection, "That... that was all inside of me?" she breathes, "I can- I can feel your semen inside of me... it's so... sticky," Yuna smiles, "Well that felt... wonderful, the textbooks were correct about that, did the sex feel good for you too?" trembling, she reaches for her notebook, already writing fervently as if your cum was not burping out of her cunt and down the side of your bed. Yuna interrogates you ferociously, asking you how tight she felt? How warm? How wet? How stimulating her vagina was compared to masturbation? Was this your first time (How adorable!)? How large your emissions were compared to normal? How quickly you would be ready for another session of sex? You blink at this last question, looking at her curiously and causing Yuna to pout, "What, did you think this is over already? We need to do several experiments to thoroughly test my hypothesis!" She sighs, whacking your cock with her pen, "Boys. Very well, shall we proceed to the second position then? Or do you require additional stimulation to become erect once more?" You shyly nod, your meat unshriveling at the thought of Yuna's touch, and she tilts her head in acquiescence while she considers what method to best use.

Yuna's head bobs steadily atop your cock, her lips locked tightly around your shaft as she sucks your erection back into being. You groan and hold onto her hair, keeping it out of the way while she does the hard work for you, her eyes narrowed in amusement while you twitch and shudder from her efforts. Yuna takes you all the way to your base, your manhood sliding down her throat, her tongue lapping quickly at your balls until her breath runs out and she pulls back. After giving your tip one final suck, her cheeks hollowing from the pressure, she relents and examines the rigid fruits of her labor, nodding in satisfaction, "Excellent, oral stimulation proved to be as effective as I anticipated," she cocks her head as she looks up at you, her puppydog eyes glistening with a hint of tears as she adjusts her glasses, "Would you say your penis regained its hardness faster than normal?" she jots down your answer before glancing back up at you, "You are paying attention right? This isn't just about your pleasure, we need to get good results for our presentation, and this helps us study for the final test!" Yuna stares in exasperation at your uncomprehending face, "You do know what the final will be on, right? Were you not listening when the teacher said what it would be on?" she smacks your thigh with her notebook, "Sex. Our final will be on sex, and I am not failing," she continues her scholarly abuse, "because my study partner was too busy getting off to help me study properly! So pay attention!" Yuna's hand curls meaningfully around your tender bits, "Got it?" she breathes, and you nod frantically, "Good, the final is in three weeks, and we have so much to test... but first..."

Your classmate wiggles her butt emphatically in the air, bent over your bed with her bottom now completely bare after she pulled her skirt up around her chest; though you would have preferred she kept it lower... "Now then, my hypothesis is that the normal degradation in penile ability caused by successive orgasms can be significantly reduced by increased sexual stimulation," Yuna monologues blithely while her pussy leaks down her sweaty thighs, "Or, at least until the built up hormones from the refractory period causes a complete collapse in your ability to sustain an erection," you grunt your assent while you rub your dick against her rear, admiring the way her waist flairs out into her surprisingly wide hips to accommodate her impressively-sized ass. Yuna continues rambling, unnoticing as your humping grows ever more needy, "This position, Doggy style, is supposedly more stimulating than the Missionary we just enjoyed, so I am curious to see how this affects your stamina and performance..." She glances back at you with a knowing smile, "You may begin, I am... excited to see how this goes as well... Can you find it this time? Here, I'll help," her fingers slither between her thighs and open her folds for you, clearly revealing where her drooling entrance was, "I want to feel your cock inside of me again..."

Yuna's supposition had been entirely correct, Doggy style was more stimulating than missionary, and it was driving you wild. You pant like a wild animal while you rut with her, the slap of her ass against your flesh was deafening while you vigorously fuck her gushing cunt. Yuna whines while you plow her, biting the sheets and moaning as your cock mercilessly tries to beat her pussy out of shape, "Oh- Mmmph! Ngh! Fuck!" Yuna grunts, "Your penis- is so- hard- this- time!" she gasps out between thrusts, "I was- right! You're so- rough!" Yuna makes an bizarre noise, and something wet splatter against your balls, "Oh fuck me! Harder! Yes!" she wails, as you continue to pound away at her from behind, a damp spot spreading beneath the site of your joining. The feeling of her soft cheeks squishing against your crotch was euphoric and you press relentlessly against it while she shoves her ass back at you with equal enthusiasm. Before Yuna had been content to stay still and let you use her like a passive onahole, but now she seemed unable to resist shoving herself back onto you; causing more than a little chaos when you both mistime your thrusts and your cock pops out of the stuffy embrace of her pussy. You waste no time in shoving your manhood back inside of Yuna, and this time after a bit of effort you both manage to synchronize your thrusts, and the steady rhythm of your sex drives you over the edge.

You nearly double over as you force yourself against the meaty bulwark of Yuna's fat ass, your cock pulsating as you unload yet another flood of cum inside of Yuna's fertile pussy. Who gasps and claws at the sheets, wailing with pleasure as your hot seed fills her once more, her back arching until it looks as if she is folded in half. This time the load you left inside of your classmate pours out of her like a waterfall, before she collapses sideways with a groan, letting your congealed juices run down her bruised ass cheek. You collapse onto the bed beside her, and this time you both cuddle in the afterglow of your copulation, while Yuna purringly informs you of her observations, "Well... I was right about Doggy wasn't I? That was... so fucking good, it felt like my brain was going numb..." She wiggles her butt against your flaccid meat, "And you were so... rough! I didn't believe the textbook when it said the presence of semen in a woman's vagina would make his sex more forceful, but... well..." she sighs dreamily, before perking up at your question, "Hmm? Oh, right, you're probably worried about that," Yuna sighs, "Well, if I was ovulating, then yes judging by the sheer quantity of semen drying in my vagina, I would have been impregnated by you. Good job! I am curious though," she muses, "I wonder how it would feel to be knocked up... for studying, of course!"

It takes around ten minutes for Yuna to finish writing her notes down, muttering to herself while she idly toys with your cock in her off-hand, seemingly fascinated by its feel. With a final vigorous motion she underlines her last statement, before looking at you and parting her pert lips, but before she can speak your phone suddenly blares, sending the both of you scrambling. You fumble for your phone' lost somewhere in the twisted sheets, and are unable to find it in time before the call goes to voicemail. Your mothers voice sighs out of the phone when you open the message, "Your father joined me for errands, and we are both now on the way home, we should be back in... twenty minutes, so try and have everything finished up by then, bye." You and Yuna share a look, her expression more than a little miffed at the obvious thought that she might not be able to record another sample, but a look of determination fills her face and she nods confidently, "Okay, this is fine. We can still fit one more test in!" she glances at you, "Start stroking while I get ready," she rushes out of the room, calling over her shoulder, "I'll be right back!" Which was about when you realize just how badly you have to pee, but when you check the nearest bathroom, you hear water running inside, evidently Yuna was suffering from the same issue, so you use your parents' bathroom to unleash what had to be the foulest-smelling piss of your life, which you were careful to flush. You returned to your room to find it empty, with Yuna dashing inside and slamming the door behind her a couple minutes later, now completely naked.

It was somewhat shocking that you had creampied Yuna twice before even seeing her tits, or for that matter, even kissing her, but those were two deficiencies she seemed eager to correct as she presses herself against you. Her lips smash into your own, and her perky breasts squish appealingly against your chest, as she wraps her arms around your neck, her body molding itself onto yours. By the time she broke off the kiss, your faces were both beet-red, your dick was somehow hardening once more. With a sleazy smirk Yuna pushes you back against your bed, kicking a stool in front of you, "Okay, this is going to be super intense, but I think I can bring you to climax about as quickly as the last time," she adjusts her glasses, "You took four minutes and forty-eight seconds by the way, a touch below average, but expected considering your lack of experience... Yuna pauses for a moment, letting you drink in the sight of her curvy form, anointed with delicate looking breasts and conversely redoubtable breeding hips, before turning and allowing you to appreciate the rear view as well. Then she steps back onto the stool, such that your erection poked against her thighs just beneath her cheeks, and grasping your dick firmly one one hand, rubs it against her sopping folds, "I'll be moving this time, okay?" Yuna informs you clinically, "I think this will go faster with me being the active one..." and promptly sits on your cock.

You shudder as your member enters the now familiar swampy confines of Yuna's cunt, her folds greeting you as enthusiastically as the first time you had visited. Your classmate rides you skillfully, or, at least you thought she was, it wasn't like you had beautiful babes bouncing on your dick regularly, but whatever she was doing still felt amazing. But even with Yuna's hips writhing down your length repeatedly, causing you to groan in time with her own squeaks, it still felt as if there was a barrier you were unable to cross, that you were unable to truly approach climax. After a couple minutes of euphoric torture, your lover notices your progress plateauing and pauses, resting her cheeks against your crotch, "Fascinating, your refractory period seems to have intensified, I wonder if we continued too soon... oh well," Yuna winks, "good thing I prepared for this!" She unmounts you slowly, leaving behind a gooey slick of fluids that coats your cock, before grabbing your manhood and orienting it back towards you. Before you can process what she was doing, Yuna was already shoving your dick into her rear hole, its entry lubricated by your shared sexual juices. If you had thought Yuna's pussy had been vice-like, her anus made her cunt feel downright loose. It felt as if her ass was trying to rip the skin off of your shaft, mercilessly crushing your manhood in its warm coils. Then she started bouncing on your cock, and your soul nearly left your body as pleasure shoots from your groin. It would take a mere seventeen seconds (Yuna would smugly inform you afterwards) of intensive stimulation from anal sex for you to orgasm, grasping Yuna's waist for support while your balls offered up what meagre sperm still remained inside of them to her insatiable anus.

This time there was little mess when Yuna removes your cock from her hole, her asshole clenching shut the moment your tip slides out of her butt. She bites her lips, clearly relishing the moment as she touches her belly, "Oh... I can feel your semen so much better in my anus than in my vagina, how odd..." she cocks her head before glancing at the clock, her eyes widening, "Your parents are already here! They're five minutes early!" Yuna bawls and she scrambles to collect her scattered clothes. You follow suit, hauling on your outfit with undue haste as you hear your front door creaking open and your mother calling up in greeting. Yuna hurriedly flips your blanket over, since there would be no disguising the massive wet marks covering it, and hops atop it, assuming a mien of supreme relaxation as footsteps stomp up the stairs. You plop down onto the floor, kicking her panties beneath your bed as you nervously pretend as if you had been typing furiously away at your laptop this whole time, and not plowing the nubile beauty reclining on your bed. You both have the merest of seconds to get your mannerisms straight before your bedroom door cracks open and your mother peers in.

You both glance up at her like startled animals, your faces flushed and sweaty, and you give her a nervous grin. Your mother quietly takes in the scene, disdaining to acknowledge the blatantly obvious evidence that something had been amiss, before her eyes bore into the slut reclining on her son's bed. Yuna maintains a façade of complete innocence, but your mom's nostrils flare, and her eyes crinkle ever so slightly in disgust, before asking glacially, "So. Did you two get much work done?" Yuna nods energetically,
"Oh yes, ma'am!" she gushes, "We got so much research done, our presentation is definitely going to be the best! We even got some studying in for the final!"
Your mother grunts, "I see. Will you be staying for dinner? We are having sausages, and I'm sure a growing girl like you would enjoy seconds..."
Yuna pouts, "Oh, I'm so sorry, but I really must be going! My big sister will be here any minute now to pick me up! But I would love to return later to sample your cooking, I'm sure it is quite delicious!" she beams endearingly.
Your mother grunts approvingly, "See that you do, I put a lot of effort into my meals..." she gives Yuna a level glare, before gifting you with an approving smile, and shuts the door behind her.

After a few minutes getting organized, and gifting your laptop to Yuna for the night so she could compile her analysis into the slideshow, the supposed slut flounces her way out your bedroom door, and almost makes her escape before your mom could catch her. You watch from the top of the stairs as your mother leans in to whisper in Yuna's ear, seeing your classmate stiffen before slightly less enthusiastically sauntering out into the night. Your mother preternaturally glances up, catching your gaze before calling, "You stink, next time open a window in there, your room was appallingly stuffy, now go shower, dinner will be ready soon!" As you hustle into your room you hear her snap at your father, "And you stop laughing! One more joke and you're sleeping on the couch mister!" Well, it sounded like you had managed to lose your virginity without your parents noticing! Adults could be so oblivious sometimes, you chuckle to yourself as you extract Yuna's panties from beneath your bed, maybe you should return these...

Yuna hums as she bounces along the sidewalk, enjoying the chill of the night against her sweaty skin until she spots her minder waiting for her. She waves enthusiastically as Yeji lurches up from her seat atop a prone figure, disgorging what sounds like a liter of semen from her cunt as she stands. Yeji greets her junior warmly, before asking as the pair wander away, "So, did you manage to get any work done?"
Yuna giggles, "Of course! It's a good thing the teacher gave us the Reproductive System, we were able to get so much research done!"
Yeji chuckles knowingly, Yuna's teachers had not required much... encouragement to adjust their curriculums to better suit her maknae's needs, "So," she sighs, "Is it love, again?"
"Of course!" Yuna gushes, "My heart was fluttering the whole time! It was so hard pretending to be all calm and studious, he was just so adorable, I wanted to eat him all up!"
Yeji ruffles Yuna's hair endearingly, "Well try not to break this one, his mom works at JYPE, and honestly her pussy kind of smells..."
Yuna huffs in annoyance, "And she was getting all mad at me for squirting all over my darling's sheets! Ugh!"

Later that night your phone pings, as Yuna sends you a message eagerly asking to come over tomorrow for some more studying. After all, her message reads, you still had to test out the sexual efficacy of her hair, hands, breasts, mouth, tongue, armpit, tummy, thighs, feet, legs, anus (again), and more compared to her vagina!

Yuna truly was a great student when it came to studying Anatomy!