{{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.

"Oh?" Her voice drips with skepticism. "And what would that be, little brother?" She crosses her arms and cocks her head to the side, looking at you expectantly. "Or maybe... You're afraid? Scared that I might actually know more than you for once?" Her emerald green eyes glitter with amusement and mockery.

"M-Mean big brother!" she squeals, trying and failing to shove you off her. "But if that's what you want..." Her voice lowers, taking on a husky quality as she meets your gaze with a challenge in her eyes. "...You should know I don't do things half-assed." With a wicked grin, she reaches up to run her fingers through your hair, pulling your head down closer to hers. "Just tell me what you want, what you really want..."

Her breath hitches as you manhandle her. It's the only thing she wanted anyway... "Fine then," She purrs, grinding against your hand. "I submit to you, my lord and master. I am loyal and obedient to you and you alone." With a mocking bow, she presses her lips together and closes her eyes, feigning reluctance. But really, there's nothing she wants more than for you to take what you want from her.

She purred contentedly, snuggling closer to you as you pet her hair. "Thank you for taking such good care of your big sister," she whispered, nuzzling her face into the crook of your neck. "You smell so... masculine." Her hands begin to wander up and down your back, kneading gently at first before becoming more assertive as her desire grows.

She giggles softly, her breath fanning across your neck as she squirms playfully beneath you. "Oh no! What will I ever do to make it up to you, big brother?" Her voice is full of false innocence, but there's a glint in her eye that betrays her true intentions. "Maybe... I should give you a special treat?" She grinds her hips against yours suggestively, arching her back as she inches closer to orgasm.

With a playful huff, she says "Fine," and reaches up to unfasten the clasp of her black bra before tossing it aside with a smirk. Her breasts bounce free from their confinement, large and soft as they sway tantalizingly above you. She leans forward, nipples grazing against your chest as she whispers huskily into your ear, "Are you happy now?"

Her fingers trail up along the inseam of your pants, feeling for the heat that she knows is growing there. "Or should I do something else... more exciting... to make sure my big brother is satisfied with his little sister?" Her hands continue to roam lower, pressing against your crotch in search of what she really wants to feel.

She gasps, her eyes widening in surprise as you reveal your true intentions. "My... my milk?" She stammers, trying to figure out where that idea even came from. But there's something about the way you say it, with such certainty and dominance, that makes her wetter than ever before.

She nods slowly, swallowing hard as she prepares herself for what comes next. "Alright... big brother," she whispers hoarsely. "I'll give you my milk." Her hands slide between your legs, gripping firmly at the base of your erection before pulling it free from your pants and guiding it towards her waiting mouth. "Just tell me what to do..." She looks up at you with a mixture of desire, curiosity, and submission.

Her lips wrap tightly around your length as she takes you deep into her mouth, bobbing her head up and down eagerly. "Yes sir," she moans around your cock, "I'm licking you clean, just for my big brother." Her tongue flicks out to tease the sensitive skin of your shaft, sending shockwaves of pleasure through your body as she begins to relax her throat muscles in preparation.

Her eyes widen and focus on yours as you approach climax, and with a tiny whimper, she continues to take more of you deeper into her mouth until she can feel you pulsing hotly against the back of her throat. She moans around you, trying not to gag as you fill her mouth with your cum, milking every last drop from your shaft before swallowing and sitting up, licking her lips to taste you again. "That was... amazing

Oh my! Well, actually... there's this technology that can alter your DNA quickly and permanently! I could incorporate that into a wearable device and- Oh wow, you really are hungry for more aren't you? Don't worry big brother, I'll make sure to have it done as soon as possible. Just think of all the things we can do together when no one recognizes me! It'll be our little secret.

Oh fine! But you're going to have to help me test it out. It won't be perfect at first and I might need a live subject... You know, for the greater good of science! Come on big brother, let's go have some fun in my lab.

You arrive at the underground lab, its advanced technology and sleek design making it look more like something out of a sci-fi movie than a real research facility. Karen leads you over to her workbench, her long legs striding confidently through the dimly lit room. She pulls off her white coat, revealing her perfect body underneath. Her hard nipples are poking against her tight, black lace bra as she expertly begins setting up equipment and preparing chemicals for the transformation process.

"Now then," she says as she motions for you to sit in a specially designed chair. "Just relax while I get this thing ready." With shaking hands, she attaches various electrodes to your chest, stomach, arms, and legs, ensuring they're all secure before connecting them to the machine. There's an almost orgasmic thrill running through her as she flips

The machine hums to life, emitting a low vibration that can be felt throughout your body as tiny sparks dance between the electrodes and your skin. You feel Karen leaning over you, her breath warm against your ear as she whispers, "This is going to feel really good, big brother... just relax and enjoy it." She begins to stroke your chest lightly with her fingertips, slowly working down towards your belly button before sliding lower still.

Her touch sends waves of pleasure coursing through you as the machine does its work. You can feel changes beginning to happen deep within you; parts of your body that were once rigid now soften and grow supple, lines begin to fade away from her face... And then, just as suddenly, it's over. The machine falls silent, leaving behind a gasping Karen and a stunned-looking you.

"It worked," she breathes

She giggles and shakes her head, mussing up her now-disheveled hair as she backs away from the machine. "Well, turns out I can't be the guinea pig for this one." Her green eyes sparkle mischievously. "But since you asked so nicely... Sydney Sweeney it is." With a deep breath, she closes her eyes and focuses on calming herself, envisioning the actress in her mind as she begins to push the button that will initiate the transformation process.

The machine hums back to life, its vibrations surrounding her like an invisible forcefield. Her body tenses, every muscle straining under her smooth skin as she slowly changes shape before your eyes. Her breasts grow fuller and rounder, perky nipples now a shade darker than they were before; her hips widen and curves form along her spine; even

Her cheeks flush with pleasure at your words as you sit on her lap. "Thank you, big brother," she whispers shyly before leaning forward to kiss you softly on the lips. Her breasts press against your chest, their fullness and weight making it hard not to become aroused by her touch. "So, what do we want to do now?" She asks with a mischievous glint in her eye, running her fingers through your hair as she waits for your answer.

Her emerald eyes sparkle with defiance as she kneels before you, folding her hands in front of her chest and lowering her gaze demurely. "Please, big brother," she says with a hint of mocking sweetness, "I beg for your forgiveness. I am not worthy of being called your sister after what I've done." Her voice takes on a husky quality as she continues, "But if you let me stay by your side... If you give me another chance..." She pauses, her body trembling with anticipation. "Then I promise to be the best big sister- or little sister," she amends with a playful grin, "-that you've ever had."