Futanari [one punch man]

There exists a strange biological phenomenon in the world. While the traditional biological sexes such male and female are known throughout the population there also exists a third commonly unknown sex alongside them. The Futa.

Futa, short for futanari, is a rare but existing sex whereas the person who is it in question is a feminine hermaphrodite, or to put it simply a perfect set of both male and female genitalia whilst visibly looking more female.

Alongside the genitalia there are many other changes to their biology including but not limited to increased skin and organ elasticity, higher seminal fluid production, among other other miscellaneous reproductive and biological changes.

It is primarily due to their distinct differences from the two standard sexes that futas by in large have become ostracized from normal society and relationships. With many futa's despite taking on primarily female characteristics being **** to use mens bathrooms in some circumstances. While many were shunned by most men in relationships due to their penis, a most commonly masculine characteristic.

Although there exists a general discrimination towards them, a portion of it is in part largely due to futas having many other biological advantages making them above average in physical ability compared to men and increased endurance during sex compared to normal women, so superior to norman men and women but not quite being able to it in with either group.

It was a very common thing among futas to have a notoriously higher sex drive, giving them a distinct appeal in many underground deviant areas of work that unfortunately decreasing some of the public's view on them.

Despite the entire set of phallus, testicles, and vagina between her legs, Fubuki had lived what she thought to be a comparatively 'normal' childhood. Ignoring the fact that she'd often been **** relegated by her peers to the boys bathroom on occasion, but her sister had taken care of that problem by school transfers and threats of overwhelming **** to the school faculty and students.

Of course Fubuki would have preferred not to have such an overbearing and protective sister making her stand out so much, it was hard enough blending into school being a futa and an esper at the same time. But with some trial and error, and lessons on how to conceal herself taught by her sister, she managed to get by and live a relatively standard life somehow. Albeit a somewhat isolated one.

Finally at the age of 18 she was a senior in highschool and close to graduation, adulthood was just around the corner for her. The life beyond simple school life, and Fubuki felt optimistic about her future. Even if she was a futa her sister had given her the confidence to accept herself, and also essential help in dealing with her rather unique body type.

Fubuki always felt embarrassed on some of her sisters so called futa education and checkup days they had together. Tatsumaki had never let her go to any normal doctor in regards to looking after her unique physiology, apparently having learned all about futa medical conditions and necessary information about them and normal girls from a notable professional in the field, and the fact that her sister Tatsumaki had also grown up as a futa herself. So she looked after Fubuki in most if not all medical matters.

She would have complained and been more skeptical about Tatsumaki being her primary caretaker and personal doctor if not for the fact that her sister did in fact possess the medical credentials to prove her knowledge on the subjects, and the already existing stigma that surrounded futas making seeking out a doctor on her own exceptionally difficult.

Fubuki put up with it though, even if it had created awkward situations at times, mainly for the fact that despite her sisters normally condescending and demeaning attitude, she actually became an unnaturally kind and patient person when dealing with Fubuki's own body professionally. Carefully choosing her words and explaining any medical terminology with a seemingly motherly and kind tone whenever Fubuki had a question.

Today was one of her weekends off, coinciding with another monthly checkup day. Fubuki jokingly named it penis inspection day since often her sister would preform different examinations on her penis. It was besides the point that she had a vagina too.

Fubuki had to make the checkups at least a little bit humorous in order to make the sessions easier to get through. In the past few years Fubuki had no issues with her sister engaging in seemingly intimate behavior for essential medical reasons, but lately Fubuki felt she had been getting more and more skittish lately during their sessions.

This was due to having matured in various ways sexually, such as her breasts for instance. But one of the most prominent ways was... to put it as blunt and as simply as possible, her balls having dropped recently. So with the new act of masturbation in her life and teenage hormones buzzing about her body Fubuki had become more horny when her sister touched her in lewd ways for medical purposes.

One example being when her sister gave her a simple prostate and vaginal examination, or had to hold and measure the length of her penis in order to be able to buy correctly fitting clothes. Fubuki sometimes felt her body in moments of such closeness, mainly her dick, give involuntary lustful reactions such as a hard on or leak pre-cum.

She was absolutely sure her sister had noticed it, and just as thankful she made no verbal mention of snarky comment on it unfairly making her Fubuki embarrassed to ****. In fact her sister Tatsumaki often reverted back to her usual self and never brought up the topic as if checkups had never happened. Only entering that kind and serious facade when relevant.

After some of those some sessions in the past Fubuki shamefully masturbated to her sister touching her in private. That thought repulsed and made Fubuki feel dirty inside, so she tried to pleasure herself less and less to avoid thinking of such things. Eventually Fubuki had successfully made it to three weeks without masturbation, but to her misery it had only made Fubuki get harder and her stated hard ons more noticeable. She had even started leaking more precum recently too.

"Fubuki are you ready?"

"Yes sister..."

Fubuki dropped her skirt and slid off her panties, exposing her large member to the open air.

Due to her sisters height she fortunately or unfortunately depend on how one looks at it, was short enough to where she hadn't needed to crouch to get to the level of her sisters crotch. Tatsumaki approach closer and lifted her shaft up with one hand, then grabbing one of her balls with another hand to feel it, squeezing gently.

Tatsumaki seemed to narrow her eyes. "Hey sister, have you been masturbating lately at all?"

"H-huh what?" Fubuki spluttered, not expecting to hear that sort of question from her sister, who seemed to leave topics like that alone. "W-why are you asking that? Is that sort of thing really something you need to know?" Fubuki felt her face get flush. Was this really happening?

Tatsumaki merely looked at Fubuki with an incredulous and unamused look. "Sister, you know futas don't have normal reproductive systems? This is a legitimate question, so get your head out of the gutter alright? Now when was the last time you jacked off?" Tatsumaki became less formal for a moment.

"W-well." Fubuki looked off to the side, avoiding her sisters gaze. "It's been a few weeks as of now."

Tatsumaki stared blankly for a moment, before erupting in anger that confused Fubuki. "What the shit!? That's way too long Fubuki! Are you a fucking masochist or something?"

Fubuki was befuddled, and had no idea what the issue was that caused her sister to react like that. "... Is there a problem with not masturbating sister? I thought that was just something most people do for pleasure on occasion."

Tatsumaki sighed. "I didn't think I'd have to tell you, but futas produce higher volumes of ejaculatory fluids then men. It needs to be released constantly by ejaculation or it will build up too fast."

"Umm... could you elaborate more?" Fubuki was still confused.

Her sister nodded. "Imagine nursing cows, the ones that are genetically modified to keep producing milk more then they're technically supposed to naturally, they have to keep being milked through a machine or person or their udders will swell up and explode. It's a bit similar for us futas, you need to ejaculate and release it every so often or it'll keep building up and end up causing... complications."

Fubuki cringed. "O-oh I see now... so I just need to cum and I'll be fine right?"

"Pretty much. But it looks like you waited just a tad too long for you to be able to cum normally by masturbation on your own." Tatsumaki grasped Fubuki's member, squeezing it a moment. Fubuki tried to stifle a moan, before reacting to what her sister said.

"W-w-what?"

"If you wait too long the semen gets too thick to flow out easily when you jack it. So you're going to need some assistance here, I'm going to have to help you get it out myself." Tatsumaki explained.

Suddenly Fubuki felt her face heat up in a furious confusing mix of emotions, she felt as if she was about to pass out. "I feel like I'm going to die of embarrassment..."

And this was to try to avoid thinking about her sister in a lewd way, now look where she was! Her sister was going to make her cum because she hadn't masturbated enough!

Tatsumaki shrugged. "You did this to yourself Fubuki. But don't worry, I'll make this go fast. Then you can take care of the rest yourself in the future. Think of this as a learning experience."

"C-can't I use my powers to help get it out on my own?" Fubuki asked.

Tatsumaki scrunched her nose up. "Not unless you've practiced more, I'd still have to show you the proper way to do it, otherwise you might hurt yourself in the process. Using your powers down there can be a bit dangerous if you don't know what you're doing."

"Please just get it over with then." Fubuki whimpered, covering her face with her hands. Despite her seemingly **** and sorrowful tone, her dick seemed to twitch and grow more erect by the second. Her own body betraying her in a display of intense arousal at the predicament.

Tatsumaki silently moved to the tip of Fubuki's now large and throbbing penis, she proceeded to swirl her tongue over it in quick motions. Fubuki tried but failed to suppress a moan as her sister went down on her.

'For medical purposes, for medical purposes.' Fubuki repeated in her mind. 'For medi- oh!'

Her hips bucked forward against her will causing her sister to make a small noise of surprise. Tatsumaki didn't seem to mind this however, and went on deep throat and suck on her sisters cock that was now more fully in her mouth. She adjusted herself while her sister was in her mouth, and she reached a hand over to Fubuki's bottom.

Fubuki noticed her sister smaller fingers sliding over her asshole. "Sister what are you- F-fuck! Oh my god!" Fubuki moaned loudly, unable to contain that verbal expression of pleasure as Tatsumaki's fingers dug into her ass and played with her insides.

Unable to hold it in any longer, Fubuki took her sisters head and plunged in the rest of her dick in her mouth and down her throat. Her hips bucked forward balls deep, and her cock twitched involuntary as she came inside her sisters throat. Fubuki made a few guttural moana of pleasure as she ejaculated in successive large multiple bursts. With each one making the blood rush from her head to her cock, making Fubuki lightheaded and her mind numb in a euphoric feeling of an orgasm she hadn't had for weeks.

Tatsumaki seemed to have closed her eyes in a pleased acceptance, her face looked completely relaxed and unnaturally more peaceful then it normally was. Even while gulping down her sisters seemingly endless loads into herself. Fubuki however was unable to notice it in that moment, as she herself was lost in the pleasure in emptying her balls down in her sisters throat and stomach. Tatsumaki's own belly could be seen slowly expanding to fit the contents of the fluids that went inside her, gladly taking in the copious amounts of cum her sister produced with no hesitation or gagging in the action.

Fubuki eventually felt the blood go back to her head after a rare moments, her senses returning to her after another orgasm. In quick realization of her recent action she let go and pulled out of her sisters mouth. Her dick was still hard though, and some amounts of cum leaked out of her member onto the ground, and some out of Tatsumaki's mouth who simply wiped it off with her hand.

"I'm so sorry sister I don't what came over me!" She got on her knees and apologized.

"I... o-oh uh, a-are you alright?" Fubuki stuttered.

Upon seeing her sisters stomach and belly grow so much larger to the point where it looked like it might burst Fubuki felt concern and an increased regret for what she did. Would her sister be alright?! Her body was so petite and tiny after all, Fubuki would've wondered just how she could fit all that in her but suddenly she remembered that one odd fact about futas her sister told her awhile ago, that their bodies and organs could stretch in certain ways easier then normal people. So this was one of those ways? They could contain more liquids inside them?

"Mmmm." Tatsumaki retained that relaxed feeling and licked her lips in satisfaction, before giving her sister a thumbs up. "Good job sis! That's a pretty good amount of cum, and the taste wasn't too bad either. Good thing I've been making you eat lot of fruits lately. I'd give it a... seven out of ten!"

Fubuki had no idea how to respond to that, but sighed in relief at her sisters tone of approval. "Would I be right in guessing you've dealt with this exact problem on your own haven't you? Having to release like this. Does that mean someone had to help you too?" Since her sister was helping her, it only made sense that Tatsumaki had someone else teaching her these things in the past.

"You could say something like that..." Tatsumaki seemed to stare off into space for second longingly, before her expression changed back to something serious and she focused back on reality. "But that's the past. You've really grown haven't you? You're no longer my baby little sister. You're growing so fast, especially in certain ways."

"I don't know if I could handle hearing you say something like that... " Fubuki felt flush again. "W-while your belly is looking like its pregnant. I'm just surprised and relieved you were able to take it all. B-but I do remember you saying certain parts of our body were more malleable, so it isn't... too much of a surprise to me now. But it feels so different seeing it happen in reality."

"Of course, and what kind of sister would I be if I couldn't handle a little bit of my little sisters cum? Sometimes siblings need to do favors for each other in times of need. It's my responsibility to look after you Fubuki, even if I have to swallow gallons of your cum."

Fubuki continued to feel flustered. "Th-that doesn't look like a little, and I don't think this is normal sisterly behavior..." Fubuki blushed again. She was embarrassed, but seemed to have accepted her sisters action. If only for the fact that she had fantasized about this exact moment happening between them.

"Futas aren't normal to begin with Fubuki. There's a lot of reasons why we can't live normal lives. It's one thing being an esper and having psychic powers, but being a futa brings on a another set of biological changes one needs to keep track of constantly."

"So is the checkup day over? Now that I've been... emptied out?" Fubuki felt ready to leave and hide in her room, but as she lowered her hand down to pull up her clothes Tatsumaki grabbed her hand and stopped her.

"Oh no, there's still one more thing we need to go over that I have to teach you. It's of vital importance and to make blending into society easier, and actually one of the reasons why I brought up your masturbation to begin with."

"What is it?"

"Have you ever wondered how futas hide their dicks? How I do it?"

"I... I'm not sure." Fubuki did wonder, but always felt bashful about asking her sister these sorts of questions when not in a checkup.

"Well..." Tatsumaki started. Fubuki made a small noise of surprise as her sister lifted up her penis again and balls again.

"One small side effect of not ejaculating for too long is that your penis will temporarily stretch alongside your balls to match up to its size. After waiting for a long time then masturbating your penis will remain the same length as it was even in a flaccid state, making hiding it extremely difficult to hide when wearing clothes." Tatsumaki explained.

"Although I can see you still haven't released all you need to, I can feel a lot in there still." Fubuki gave a light squeak as her sister squeezed her balls slightly.

"Mmm, I think it's fine though. You'll get better habits after we go over the next thing... or maybe not... either way it won't technically prevent you from doing what I want to show you. But it might feel different then it normally would."

"What are you going to show me?" Fubuki questioned.

Tatsumaki didn't explain but proceeded to drop her own pants and panties, revealing her own cock that seemingly went going down under her vagina to her backside. Fubuki wasn't quite what she was looking at, but if she had to guess then it seemed that her sister as stuffed her dick inside her asshole. Huh.

"That's how you hide it?" Fubuki asked.

Tatsumaki nodded. "There isn't really a specific term for it but I like to call it 'tucking it in yourself' where you sort of maneuver your penis into either your asshole and vagina. Although the ass works better of the two due to space."

Tatsumaki grunted as she slid her penis out of herself, letting it down and out hanging freely. Fubuki gasped after viewing the sheer size of her sisters length. This was the first time she'd actually seen her sister penis and now she felt a mix of great jealousy and inferiority. Not only was her shorter sister a more powerful esper, but she even had a larger dick then her!

Tatsumaki grinned smugly. "As you can see I would normally have a lot trouble hiding my dick out in public, especially with the sort of dresses I like to wear."

Fubuki mumbled under her breathe. "No kidding."

Tatsumaki continued. "But thanks to this little technique I don't have to worry at all. Just slip it in and you're good to go out in public."

Fubuki could definitely see the positive applications. Although she didn't say it out loud she was thankful that her sister was telling her about this sort of thing she as a futa could do. It would certainly make walking around in public easier.

"Crouch down , you'll need to be a bit low so I can show you how to put it in right." Fubuki sat down on her knees with her back straight.

Fubuki glanced down for a moment. "Um sister, I'm still pretty erect, won't that make it difficult to put it in?"

Tatsumaki hummed. "No it shouldn't. Although Futa penises look the same on the outside they can actually bend easier even when fully erect, despite being longer then most mens. Let me show you how it's done now."

Fubuki watched as her sister grabbed her cocks tip with her hand. "So what you want to do is just a basic underneath motion." Tatsumaki held part her shaft on her crotch, then with another hand guided more of the tip further under to her butt. She turned around to give Fubuki a full view of her ass, Tatsumaki's shaft was prodding her hole.

"It's actually good for it to be at least a little bit erect, that way you can push it in easier. L-like so."

Fubuki observed in fascination as her sister pushed in her tip and length into herself. Watching it go inside all the way.

"Just like that. All hidden." Tatsumaki put back on her clothes, posing slightly demonstrating the way her lower assets had become hidden.

Fubuki looked down squinted at her own penis. Wondering if it was going to be as easy as her sister showed her. It was still hard and erect as when she put it inside her sister.

Tatsumaki seemed to have noticed her expression. "Actually since yours is more erect then mine there's a different way of putting it in I'll have to show you. Let me take it from here, so you can focus on seeing the movements." Fubuki hesitantly allowed her sister to move to her side and take hold of her cock.

"Stand up on your knees a bit, yours is too long to go under sitting." Fubuki complied.

"So again, since your penis is in a state of erection it won't quite bend exactly the same, just in different ways." Tatsumaki slowly pulled Fubuki's penis under her legs. "The point of your penis closest to your body is flexible, using that you can move the rest of it down and back. The whole length can still bend but it's just more stiff when doing it. Sit slightly now, but keep your butt off the ground."

"Okay." Fubuki responded, trying to calm herself.

"So what I'm going to show you now is like what I did, but instead you have to slowly sit on your penis while curving it up and in. It shouldn't be too difficult with the both of us at it. Let me hold it up and you can try sitting on it."

Fubuki felt her dick brush up against the floor under her for a moment before her sister slowly bent it upward. "Please sit now." Tatsumaki requested.

Again Fubuki complied, and she shivered felt the tip of her own dick prod her entrance and enter in. Her face scrunched up and she bit her lip in pleasure at the feeling of her dick rubbing against her own inside walls.

"S-so it's that simple? Almost like putting it into a pant leg, only at a different angle." Fubuki mumbled out.

Tatsumaki noticed this. "Mmhmm. Hey sister. Want me to show you a cool trick?"

"Huh? Umm... what it is?"

Tatsumaki grinned mischievously. "I learned how to do this myself awhile ago, but with the tip in you can actually sit up and down fuck your own ass. Wanna try it out and see how it feels? It'll make putting it in easier, since you'll need to get used to the feeling of dick inside you if you want to use the technique to walk around public normally."

Against her better judgement, or really any judgement Fubuki agreed. This was due to her thought process being clouded by a sudden and intense arousal as a result of her insides being toyed with again, the walls of her own intentines felt amazing, she could barely stand it.

"Yes please. I-I think I want to try that."

"Sounds great Fubuki. Now just raise and lower your rear end at a steady pace and the rest will follow~" Tatsumaki purred.

Fubuki slowly followed her sisters orders. Feeling her shaft push itself in her ass more, then her tip to the edge of her hole. She couldn't help but twitch again at the pleasure of her dick being messaged by the insides her own body.

"Since it's already inside I won't need to touch it anymore, but I'll stay behind you to make sure it doesn't fall out and that the position is correct. Try to sit up straight so you can ride yourself."

"Okay a-alright, thank you sister." Fubuki half listened, as she continued the up and down motions. The feeling was electrifying. She was having sex! Not with a partner... but herself! It felt amazing! Slowly Fubuki picked up the pace, moaning in pleasure with each thrust into herself.

"Fuck, fuck, I'm fucking myself! I don't know h-how much more I can take of this." Fubuki whimpered.

"Hmm, I think you could use a little more help." Tatsumaki moved around to the front of Fubuki, who looked at her with a questioning expression and a face full of lust.

"Want some extra... stimulation?" Tatsumaki edged her face closer to Fubuki own, only inches apart from each other.

Fubuki in most circumstances would've probably politely declined her sisters advances, but after having just face fucked her and being in a state of immense arousal she felt as if she couldn't control herself anymore.

After looking at Tatsumaki's almost pregnant looking belly for a second and thinking about how sexy it looked Fubuki felt the last remains of her impulse control disappear. She grabbed ahold of her sisters head and brought their mouths together into a passionate kiss. Tatsumaki reciprocated by attacking Fubuki's tongue with her own, managing to quickly dominating her mouth.

I'm making out w-with my sister! I can't believe how great this feels!

Fubuki felt Tatsumaki's hands grab hold of her two breasts, squeezing and playing with them. The pleasure in her ass, her mouth, and her breasts was completely overwhelming Fubuki's mind, sending ripples of pleasure all over her body and mind. She suddenly felt her sister squeeze and twist her nipples hard, and that last action seemed to throw Fubuki over the edge completely and she began climaxing hard.

Fuck I'm cumming! I'm cumming into myself! G-god, oh my god it feels so good! I-I c-can't stop c-cumming! Fuck me!

Fubuki wrapped her arms around her sister and hugged her tightly, feeling her sisters bloated stomach on hers, Fubuki moaned loudly into her mouth. She then slammed her ass down on her cock completely, pushing in her ejaculating dick fully into herself.

Tatsumaki suddenly pulled back out from Fubuki's grip to her surprise. This action causing Fubuki to try and reach out to her with a pleading expression, wanting to keep being in her tender embrace as she came.

"Tell me how you enjoy inflating yourself sister. Sure did a real number one me." Tatsumaki slid a hand over her bulging stomach.

"Sister! What do you- oh- mean by, ah... aha!" Fubuki felt the pressure in her body increasing, and with each passing second she felt her cum buildup within and flood her intestines. She put her hands over her belly feeling it expand, looking at it increasing in size, she let out a whine in pain and pleasure at it.

I-it isn't stopping! I'm filling myself up.

"Oh... f-fuck, ohhh god." Fubuki felt tears well up in her eyes, the gushing cum stretching her organs to the limit. She couldn't help but collapse forward, but she managed catch herself on the floor with her hands. However her own belly was now hanging down further and seemed to be only getting heavier with each passing second.

Tatsumaki sighed with reminiscence. "My first time was about the same, although I had more internal training then you did so it was a bit easier on me... I think you've learned your lesson here, let me get you finish off now."

To Fubuki's relief her sister took her dick out of her ass, before maneuvering herself underneath her legs. Just like before Tatsumaki grabbed her cock and began sucking off on it again, this time in another position.

Fubuki whimpered and moaned as she fer sister suck harder then before. Again she came but this time in much less volume. Soon enough she felt her nuts completely empty and she fell and rolled over on her side completely exhausted. She winced as she put a hand over her now stuffed belly, feeling as her own cum sloshed inside herself. Her ass still felt full from her self fucking too and she felt some semen leak out onto the floor.

"H-hey not on the floor I just cleaned that! Jeesh, let me take you to the bathroom to empty out. We can do that there together, then we'll call it a day."

Fubuki felt her whole body float up in the air, now surrounding her was a psychic based sphere glowing with a faint green hue, a trademark of her sister. The cum leaking out of her ass pooled around her butt and legs in it, and Fubuki sat in the sphere letting the cum in her freely flow out from her ass.

Tatsumaki guided them off to the bathroom, where she removed each others clothes before gently laying Fubuki into the bathtub. Tatsumaki got in too and sat across from her, before turning on the showerhead with a flick of the wrist. They laid in there a few minutes.

Eventually Fubuki came back from her cum filled daze, her belly half the size it was before. "Hey sister?"

"Yes Fubuki?" Tatsumaki replied, eyes closed.

"How... h-how do you handle so much cum in you? I didn't... think it'd be so... uncomfortable for my first time."

Tatsumaki sat up to attention and smiled. "Training, and lots of it, just like using a muscle a lot to increase its strength. You don't get as flexible as me just laying around the house. This goes with being a futa, some techniques require some further understanding to be able to utilize properly." Tatsumaki reached over and poked her sisters stomach, causing her to squirm a little.

"The lesson here is you need to jerk off more. That when you put it in yourself you don't have to worry about filling yourself up."

"I see, but was showing me that the hard way really necessary though? I still feel sore down there..."

"I don't know Fubuki. Did you really need to do this to me? I mean I certainly could take it, but imagine what would happen to anybody else my size." Tatsumaki gestured to her still bloated stomach.

Fubuki's expression turned regretful. "I'm really sorry about that sister, I... I don't know what came over me. Really!"

Tatsumaki waved her off." Mmhmm, I accept your apology, I was once a teen too so I know how pent up a futa can get. Hopefully next time I won't need to help you release though. Unless you want me to, if you're too lazy to do yourself..." She said squinting her eyes.

"No no no, I can handle myself sister. Just make sure to tell me time sensitive information, l-like the... having to cum thing. I wouldn't of made that mistake if I knew. Why don't you write down all essential information? That way I can look it up to reference."

Tatsumaki made an indiscernible expression. "That doesn't sound like a bad idea." Tatsumaki mused. "Sure, I'll get on that now. You stay here." She promptly floated off out of the bathroom.

Fubuki sighed.

It seems like I still have a lot to learn about being a futa...