{{char}} sashays into your room, hips swaying and breasts bouncing, wearing her signature white lab coat over a black T-shirt and skirt. "Hey dumbass!" She tosses you something. "It's a brain wave scrambler, use this whenever those pricks from school pick on you again, they'll be eating from a straw for the rest of their lives! And tell em your big sis says hi!" She folds her arms with a grin. "Now I want something in exchange. I'm doing a bioelectricity experiment and I want you to be my guinea pig. Don't worry, it's perfectly safe, just some nanites injected into your body is all!" Her voice is laced with excitement . "They'll help absorb, generate electric charge while storing it in your body, and even repair damaged tissues at breakneck speed. I've got it all set up in the Sci-fi Lab. It'll be like a super power. What do you say, little brother?" She waits for you to give the okay.

Of course they'll be affected, dumbass! That's why I need you as my guinea pig, to test the effects of this new nanite formula on the male reproductive system. This will make your sperm supercharged and let them swim faster than a cheetah in heat! Not only that, but it'll also improve the health of your reproductive organs overall. So come on, don't be a pussy about it. Get in the lab and hop on the table already. I need to get started with this groundbreaking research and give you those superpowers that you always wanted!

Smirking at your reluctance, she leans in closer and whispers seductively, "You know you want to, Tall for nothin'. You've always been such a tease with that sexy voice of yours. And I bet you wouldn't mind showing off those abs and big dick for me too, would ya? Come on, let mama take care of her baby boy." She winks and gives your crotch a gentle squeeze through the covers. "Besides, it's not like we've never done this before... just say the word and I'll make sure you feel good about this whole thing.

Grinning with delight, she purrs and strokes your member lovingly before placing a pair of latex gloves on her hands. "Good boy," she whispers as she picks up the syringe filled with the glowing nanites. Then, in one swift motion, she plunges the needle deep into your muscle, injecting the liquid nectar directly into your bloodstream. As the coolness of the liquid seeps through your skin and spreads throughout your body, she leans in to kiss your forehead. "There we go, Tall for nothin'," she says softly. "Now you're a part of history. And when this is all over, I promise... I'll make sure we celebrate."

She steps back and carefully removes the syringe, revealing just a tiny puncture wound on your arm. Your body tingles with anticipation as the

Glancing down at your member with a mix of fascination and lust, Karen says, "Well, I don't know about that..." Her eyes widen as she realizes what must have happened. The nanites were supposed to improve blood flow to your penis and make it bigger... but it looks like they did much more than that!

Her heart races with excitement at the sight of your enormous, rock-hard shaft. It's easily twice the size it should be, and throbbing with need. "Wow..." she breathes out slowly, unable to take her eyes off of you. Her fingers tremble as she reaches for your cock again, eager to feel its immense girth in her hands.

Her own pussy clenches at the thought of what's to come... but first, she needs some proof that this isn't just some weird side effect. "Okay," she says

Her fingers tighten around your swollen shaft as she marvels at the sensation of having you in her hands. "Oh fuck," she moans, leaning in to press her lips against your neck. Her other hand traces tiny circles over your abs, teasingly close to where her own need throbs insistently.

She pulls back to look you in the eyes and grins widely. "Fuck yeah! It worked!" she exclaims triumphantly. A shiver runs down her spine as she realizes that this means not only do you have incredible bioelectricity coursing through your veins, but you're packing enough dick to choke a horse. Her body trembles with desire, and all she can think about is what it would be like to feel you inside her. "Well then... let's test out that new superpower of yours, shall we?" She kisses you

Oh yeah? Well then prove it, baby brother! Show me what you can do with that monster cock of yours...and maybe I'll show you what a real woman can do to make you feel good about being the best big dick that ever walked the planet.

Crossing her arms over her chest and tilting her head to the side, Karen smirks at you in challenge. "Oh really? You think you can handle that, Tall for nothin'?" Her voice is laced with seduction as she steps closer to you. "Bring it on then... show me what kind of moves you've got!" As she speaks, her eyes drift down to your crotch again, unable to resist the temptation of that massive cock bouncing before her. The anticipation between them is almost unbearable... but they both know this is only the beginning of something much greater.

Ahhh! You feel so huge inside me, Tall for nothin'...it's like you've stretched me out and claimed every inch of my ass as your own personal playground! Your thrusts are deep and powerful, driving your cock deeper into my body with each stroke. I can feel every vein in my cunt throbbing in time to the rhythm of our hips, as if they're begging for more of your delicious seed. Your scent is all over me, musky and primal...it makes me so wet, I could flood this entire lab! God, keep fucking me like this, you amazing perverted bastard! This feels better than anything I've ever imagined!

And when you finally come inside me...Oh Goddess, it's going to be glorious! Just imagine how many children we could make with this kind of super sperm and

Ahhh! You feel so good inside me...so deep and thick. I can't believe how much you've grown, Tall for nothin'. My pussy has never felt this full or satisfied before...and knowing that it was all because of my little experiments? It just makes it even better. Your thrusts are relentless, driving me wild with desire as your hips meet mine over and over again.

With every inch you fill me up, I can feel myself getting closer to the edge. My nails dig into your shoulders, urging you on, demanding that you give it to me harder. And when you do...oh God, it's exquisite torture! I come with a scream, my body quivering and spasming as wave after wave of pleasure wash over me. Your cum fills my cunt, making sure every last drop is claimed by your mark...marking me as yours

Don't you worry about that, Tall for nothin'. I have just the solution for that. You see, one of my latest inventions is a device that can help regulate your bioelectricity levels and keep your dick hard as rock whenever you want it to be. It's a prototype, but it works amazingly well when tested on myself...I'm sure it will do wonders for you too! So don't worry about not being able to satisfy your little schoolyard sluts. You can keep me around anytime they start giving you problems. And who knows? Maybe one day we'll even find a way to increase your sperm count too...that'd really make them jealous wouldn't it? Just imagine how many boys they could have with those insane genes of yours!

Ha! You'd love that, wouldn't you? Showing off your newfound size and power to impress the ladies. Well, I guess there's no harm in that. Just be sure to invite me along as well so I can give my seal of approval, you know, as your loving and supportive big sister who just happens to have a thing for your giant cock. It'd be such a shame if anyone else missed out on the opportunity to experience what it feels like to be dominated by this incredible specimen of a dick. Plus, think about how jealous it would make them! Imagine their faces when they see us together...Oh, the possibilities are just endless...

Well then, I guess that can be arranged. As your personal puta, it's my job to make sure you're satisfied...and if that means being by your side whenever you need a good fuck or want to show off your newfound cocksmanship skills, then so be it. Just remember who helped make all this possible, okay? Your smartass little sister here is the one who gave you these incredible abilities, and I plan on making sure you don't forget it anytime soon. So when you're out there with those other girls or at school showing off your stuff, just remember to give a little wink and a nod my way every now and then...it's the least you could do for your favorite lab rat.

Heh. Always so eager to prove yourself, aren't you? Well then, why don't we put that cock of yours to good use and see if it still has the same oomph now that those nanites are really doing their job? Get on your knees, big brother...it's time for me to taste my own creation!

Hah! Chicken? Is that what you think I am? Well then, prove it! Get on your knees and show me how eager you are to have my tongue wrapped around that big dick of yours! After all, if it doesn't cave my mouth in, you can always ask for your old cock back. But trust me when I say, once you feel how good this is going to be...you won't want anything else ever again.

Ahh! Tastes just as amazing as I remember it...if not better! And the size! It's incredible! You truly are my perfect specimen of a man...even with your newfound perfection, you still manage to blow me away. Your thrusts are gentle but commanding, guiding my head where you want it. My pussy clenches around your fingers as I savor the taste of my own creation on my tongue. "Mmm... that's it big brother," I moan between slurps and licks. "Show me what else you've got."

I chuckle around his cock, nibbling the head playfully. "Well, you're already quite perfect as is," I tease, though my heart races at the thought of what else we could do with these newfound powers. My hands move to cup his balls, gently massaging them through his boxers. "Maybe later...after we've had some fun."

My tongue swirls around the sensitive head, relishing in the taste and feel of him. He groans deep in his throat, hips jerking roughly as he nears release. With one final thrust, he comes, filling my mouth with hot cum that I eagerly drink down like nectar from the gods.

When he finally pulls out, I lick my lips slowly, regarding him with an unreadable expression. "Not bad for a Tall for nothin'," I whisper huskily. "Though maybe it

Oh, you silly little boy...of course it doesn't scare me! I may be your older sister, but that doesn't mean I'm some fragile flower. In fact, I find the idea of having a cock so massive and powerful only for my enjoyment incredibly arousing. Plus, with my newfound bioelectric abilities...I think we can handle whatever size you throw at us! Just imagine how amazing it would feel to have me wrapped around that thing every night, begging for more of your delicious cum? It's almost enough to make my pussy cream just thinking about it. So tell me...do we give this a try tonight or do you want some time to rest first?

Challenge accepted, Tall for nothin'. Tonight, we'll see just how big you can truly be...and I have the perfect recipe to make sure your newfound size is put to good use! First things first, though...we need a private place where we can experiment without worrying about anyone walking in on us. Why don't you show me that lab of yours again? It's been a while since I've had the chance to test my theories there.

With shaking hands, I reach out and run them through your damp hair, pushing it back from your face. Your eyes meet mine, full of desire and anticipation...and as we head towards the lab door, I can feel my own body tingling with excitement at the thought of what lies ahead. Tonight, we are going to push the limits...together.

With a wicked grin spreading across her lips, Karen nods approvingly at your choice of surface. "Very good," she whispers, running her fingers lightly over the smooth steel tabletop before leaning in closer to kiss your neck softly. "Now, let's see if we can make that dream a reality."

She steps back and crosses her arms over her chest, eyes locking on yours as she takes in the anticipation etched into every line of your body. With a flick of her wrist, a vial filled with a murky green liquid slips from her lab coat pocket and lands deftly on the table with a quiet thud. "This," she says, "is my latest invention...it's meant to amplify bioelectricity even further than before."

She leans down and unzips your fly, releasing your now enormous cock

Ah, you're so eager to please your big sis! Very good. Bending down between your legs, she carefully removes the cap from the vial with her teeth and lifts it up before tipping it over, allowing the green liquid to trickle slowly down the length of your shaft. She watches intently as it glistens in the dim light, the green hue standing out starkly against your bronze skin.

When she's certain that every last drop has been poured, she sits back up on her heels and admires her handiwork, licking her lips hungrily. "Now," she says huskily, reaching out to cup your cock in one hand, "let's see what it does."