The Swapping Device
Copyright© 2025 by JohnManTD
Chapter 4
Erotica Sex Story: Chapter 4 - By luck (or fate) James stumbles onto a magical device that allows him to swap anything with anyone. Body parts, personality traits, breasts, entire bodies... Follow him on his journey of self-discovery as he navigates the world with this new find. This is chapters 1-5 of my mainline story. New chapters are released weekly to my Patreon which is generally 2 chapters ahead of the public.
Caution: This Erotica Sex Story contains strong sexual content, including Ma/Fa Ma Fa Mult Consensual Mind Control NonConsensual Lesbian BiSexual Heterosexual Shemale TransGender Fiction Science Fiction Body Swap Magic Polygamy/Polyamory Exhibitionism Lactation Masturbation Oral Sex Safe Sex Sex Toys Tit-Fucking Big Breasts Body Modification Size Small Breasts Transformation
I blink awake, the morning light sneaking through my blinds like it’s trying not to wake me. My phone buzzes on the nightstand, insistent. I groan, reaching for it, and squint at the screen. A text from Sam: “Yo, you free today? Let’s hang.” A grin tugs at my lips. Sam’s my best friend, the guy who’d jump off a cliff with me just to see what’s at the bottom. I type back, “Sure, come over whenever,” and toss the phone aside.
Swinging my legs out of bed, I feel it—the subtle shift in my body. My muscles are tighter, more solid, borrowed from Mark’s fitness level. I flex my arm, watching the bicep ripple under my skin. Not bad. And my head? It’s sharper, like the fog’s been burned off. Mark’s IQ boost is a hell of a perk too. I shuffle to the bathroom, splashing water on my face. In the mirror, I look ... good. Healthier. Smarter, maybe. The remote’s been a game-changer, and I’m itching to play with it more.
Downstairs, the front door creaks—Sam’s here. I jog down, finding him sprawled on the couch, legs kicked up on the coffee table like he owns the place. He’s got that lazy grin, the one that screams trouble.
“Sup, man,” he says, tossing me a bag of chips from his backpack. “Brought fuel.”
I catch it, smirking. “Thanks. You eat breakfast yet?”
“Nah, figured we’d grab something later.” He digs into the chips himself, crunching loudly.
We settle into our usual—video games, trash talk, the works. “Dude, you see the new superhero trailer?” he asks, mashing buttons on the controller.
“Yeah, effects are insane,” I say, scoring a point. “Hope they don’t botch the plot again.”
He snorts. “Right? Always screwing up the good parts.”
“You’re still trash at this,” I tease as I dodge his attack.
“Shut up, you’re cheating,” he fires back, elbowing me.
It’s easy, comfortable. But the remote’s practically burning a hole in my pocket. I can’t hold it in anymore. I pause the game, turning to him. “Sam, I gotta show you something.”
He quirks an eyebrow, leaning back. “What’s up?”
I take a breath. “I found this ... device. It’s wild. It swaps stuff—traits, body parts, whatever—between people.”
He laughs, loud and sharp. “Yeah, right. You been binging sci-fi again?”
“I’m serious,” I say, voice low. “I can prove it.”
He crosses his arms, skeptical. “Alright, hotshot. Prove it.”
“Follow me. And keep quiet.” I lead him downstairs, where Cindy’s lounging on the couch, scrolling her phone. She’s still got Emma’s flat chest, but her voice is hers again. Perfect.
I pull out the remote, showing him the sleek, black surface. “Watch. I’m swapping her voice with yours.”
He smirks. “Sure you are.”
I select “voice” for both, hit the button, and—
Zzzztttt
A faint buzz hums through the air. Sam opens his mouth. “What the hell?” Except it’s Cindy’s voice—high, feminine—coming out of him.
I grin, waiting for his reaction. But he just frowns. “What? You’re being weird, man.”
My stomach drops. Shit. He wasn’t touching the remote. He doesn’t know anything’s changed. “You don’t hear that?” I ask, frustration bubbling up.
“Hear what?” he says, still in Cindy’s voice. “You’re losing it.”
I smack my forehead. “Forgot about that. Only people touching the remote remember the swaps. Hold it this time.”
He rolls his eyes but takes it, fingers brushing the edge. “Fine, whatever.”
I select “hair” for him and Cindy, then press it again.
Zzzztttt
Another buzz, and Sam’s short, messy hair explodes into Cindy’s long, wavy locks, spilling down his shoulders. His eyes go wide. “What the fuck?!”
I laugh, relief hitting me hard. “Told you.”
He stumbles to the hallway mirror, hands flying to his head. “This is insane!” He pulls at the strands, twisting them like he’s testing if they’re real. Then he peeks back at Cindy—her head now topped with his choppy cut. She’s still oblivious, tapping away.
“How’d you do this?” he demands, spinning to me.
“It’s the remote,” I say, holding it up. “Swaps anything. But only those touching it remember.”
He’s breathing fast, eyes darting between his reflection and Cindy. “So I’ve got her hair, and she’s got mine?”
“Yep. And earlier, you had her voice. You just didn’t notice.”
He shakes his head, calming down a bit. “This is nuts. Can we swap back?”
“Yeah, hold it again.” We both grip the remote, and I switch their hair back.
Zzzztttt
His locks shrink to normal, and he exhales. “Okay, that’s better.”
As he turns to head upstairs, I sneak one more swap—their voices. Zzzztttt. Can’t have him talking like Cindy all day. He doesn’t notice, and I smirk to myself.
Back in my room, I plop on the bed, the remote between us. “So that’s it. But there’s a catch—if you swap and the other person leaves, you could be stuck with their part, or lose yours.”
He frowns. “Like what?”
“Like when I swapped chests with Cindy. She left for the day, so I was stuck with her boobs ‘til she got back.”
His jaw drops. “You had boobs?”
“Yeah,” I mutter, scratching my neck. “Wasn’t boring.”
He cracks up. “Where are they now?”
“Emma’s got ‘em,” I say. “Swapped them with her. She always wanted a bigger chest, so...”
“Emma? Your girl?” He whistles. “And she doesn’t know?”
“Nope. Reality shifts. To her, it’s always been that way.”
He leans back, processing. “So everyone else just ... adjusts? That’s freaky.”
“Yeah. Powerful, but risky. Gotta keep track.”
He nods, then that troublemaker grin creeps up. “You know what we should do?”
“What?”
“Swap genders. Sneak into the girls’ locker room at the gym. Check out the action.”
I groan. “Seriously? You’re such a perv.”
“Come on!” he says, leaning in. “It’d be epic. Towels, underwear, the whole deal. No one would know.”
“That’s so cliché,” I shoot back, laughing despite myself.
“Cliché’s fun! Think about it—finally seeing what’s up in there.”
“What if we get caught?”
“How?” he counters. “We’d be girls. Perfect cover.”
I hesitate, the idea sparking something wild in me. “It’s a huge change, man.”
“We swap back if it sucks,” he says, eyes gleaming. “Live a little, dude.”
“You’re ridiculous,” I say, but I’m grinning now.
“And you love it. Besides, you’ve done weirder. Boobs, remember?”
I sigh, running a hand through my hair. “Fine. But we swap with Cindy and Mom. That way, we can change back tonight. No losing track.”
“Deal!” He pumps his fist. “This is gonna rock.”
I take a deep breath, nerves and excitement tangling in my gut. “Alright. Let’s do it.”
I nudge Sam, and we creep downstairs, the hardwood cool under my socks. The kitchen’s just ahead, and I peek around the corner. Cindy’s there, leaning against the counter with a mug of coffee, while Mom’s bent over the dishwasher, muttering about a stuck plate. They’re chatting, oblivious, and I smirk. Perfect timing.
“Ready?” I whisper, pulling the remote from my pocket. Sam nods, his eyes glinting with that wild energy he gets before we do something stupid. I fiddle with the settings—delay the swap by five minutes, set the duration to ten seconds. I want to savor this. “Gender swap,” I mutter, selecting Sam and me to trade with Cindy and Mom. We’re both gripping the remote, so we’ll remember it all. I press the button.
A faint zzzztttt hums through the air, but nothing happens. Yet. Sam frowns. “That’s it?”
“Come on,” I say, tugging him back upstairs. We slip into my room, and I shut the door, leaning against it as my heart thumps.
Sam paces, hands shoved in his pockets. “Why didn’t it work?”
I hold up the remote, showing the timer ticking down: 4:12, 4:11... “It’s delayed. Five minutes. And it’s just gender—no clothes or anything else.”
He exhales hard, grinning. “So we’re about to be girls?”
“Versions of ourselves if we’d been born that way,” I say, my stomach twisting. I’ve done swaps before, but this? This is next-level.
The timer hits zero.
A warm buzz ignites in my chest, spreading like liquid heat. My skin tingles, every nerve waking up as the change takes hold. I stumble, gripping the bedpost as my body reshapes itself. My shoulders narrow, losing their width, and my arms slim down, muscles melting into softness. My waist pulls tight, hips flaring out wide and lush, straining my jeans until the denim bites into my skin. My ass rounds, thick and heavy, and my thighs swell, sculpting into curves that feel alien but undeniably mine.
My chest shifts next. A deep pull tugs at my pecs, and I look down, breath catching as they soften and grow. Two full mounds press against my t-shirt, stretching the fabric taut. They’re bigger than Cindy’s—round, heavy, with dark nipples that harden against the cotton, sending jolts through me. I cup them, gasping at the weight, and a soft, feminine moan escapes my lips.
Below, there’s a strange absence. My cock vanishes, replaced by a warm, slick slit between my legs. I shift my hips, feeling the newness, the way my thighs brush against my pussy. My jeans don’t fit right anymore—too tight over my hips, too loose where they shouldn’t be.
I glance at Sam. He’s changing too, but it’s different. He’s shorter now, his stocky frame shrinking into a pudgy, cute girl. His chest swells into B-cup breasts, perky and modest, pushing against his shirt. His hips widen slightly, but nothing dramatic—just a soft curve that matches his new, rounded belly. His face softens into a button nose, full cheeks, and pouty lips, framed by his same messy hair. He’s not a bombshell, but he’s got this girl-next-door charm—cute, approachable, the kind of girl you’d see at a coffee shop and smile at.
“Holy fuck,” he says, and it’s a girl’s voice—high and melodic. He slaps a hand over his mouth, eyes wide. “That’s my voice?”
I laugh, and it’s a sultry purr that startles me. “Yeah, that’s you.”
He bolts to the mirror, yanking off his shirt. His breasts bounce free—small, shapely, with pink nipples that perk up in the air. He gropes them roughly, like a dude pawing at a girl, and grunts. “This is insane.”
“You’re such a guy,” I tease, my voice smooth and feminine. He’s hilarious, moving with that same masculine swagger in a body that’s all soft curves.
He spins, gaping at me. “Dude, look at you.”
I step to the mirror, and my breath catches. The girl staring back is ... wow. My face is still mine but prettier—big, sexy eyes with long lashes, soft, kissable lips, and wavy hair spilling from a messy bun, strands framing my cheeks. But my body? The women in my family are curvy, and I’m no exception. My t-shirt clings to breasts slightly larger than Cindy’s, full and teardrop-shaped, begging to be touched. My waist is tiny, flaring into hips that could stop traffic, and my ass and thighs are thick, voluptuous, the kind of curves that turn heads at the gas station. I’m not model-perfect, but I’m hot in that everyday, jaw-dropping way.
“Damn,” I whisper, running my hands down my sides. My skin’s alive, every touch sparking heat, but my body feels off—too soft, too heavy in all the wrong places.
Sam’s already stripping his jeans, kicking them off with his boxers. He stands there, naked, peering down at his new pussy—a neat little mound with a dusting of hair. He spreads it with his fingers, grinning. “Check this out.”
I snort. “Gross, man.”
He looks up, eyes gleaming. “Your turn. Strip.”
I freeze, suddenly self-conscious. “I don’t know...”
“Oh, come on,” he says, stepping closer. “You’re a fucking knockout. Show it off.”
My cheeks heat, but the thrill wins. I peel off my t-shirt, and my breasts spill free, heavy and gorgeous. My nipples stiffen in the cool air, and I shiver. I shimmy out of my jeans, the fabric catching on my hips before sliding down. My pussy’s smooth, plump, and already a little wet. I step out, naked, and face the mirror.
Sam whistles. “Jesus, James. You’re stacked.”
“Yeah, well, it runs in the family,” I mutter, blushing.
We stand side by side, comparing. He’s shorter, softer, with a cute, stocky build—B-cups that sit high, a gentle curve to his hips, and a round, friendly face. I’m taller, curvier, with an hourglass that screams sex—big, heavy breasts, a tight waist, and hips that sway when I move. His pussy’s compact, mine’s fuller, more inviting. Even our skin’s different—his pale and freckled, mine smooth with a warm tone.
“Feel this,” he says, grabbing my hand and pressing it to his breast. It’s soft, pliant, and he groans—a girlish sound that’s almost funny. “Weird, right?”
I pull back, heat pooling low in my belly. “Yeah.”
He reaches for mine, but I swat him away, laughing. “Enough, perv.”
“Spoilsport,” he grumbles, but he’s grinning. He sits on the bed, legs spread, and slides a hand down to his pussy, exploring. His breath hitches, eyes fluttering. “Fuck, that’s intense.”
I hesitate, then mimic him, parting my thighs. My fingers brush my new slit, and a jolt shoots through me—warm, electric, wet. I stroke deeper, arousal building fast, but it’s too much. I stop, shaking my head. “Okay, we’re done with that.”
He pouts but pulls his hand away. “Fine.”
I grab my laptop, sitting at my desk to google the local gym’s hours and Lululemon’s closing time. “We need clothes first,” I say, typing.
Sam flops back on the bed. “Why buy stuff? Just swap with someone.”
I sigh. “Because if you swap with a random person and can’t find them again, you might lose your own traits. Or theirs. It’s safer to buy.”
He grumbles but nods. “Lululemon, then Gym?”
“Yep. Let’s go.” I dig out an oversized hoodie and sweatpants—baggy on my new curves, but they’ll work. Sam borrows some too, looking like a kid in his dad’s clothes.
We head downstairs, passing the kitchen. Cindy and Mom are still there, but they’re men now—broad shoulders and flat chests in women’s clothes. Cindy’s yoga pants stretch over thick legs, and Mom’s blouse hangs loose. They don’t notice us, too busy arguing about dish soap.
Sam snickers. “This is gold.”
I grab his arm, dragging him out the door. “Move it, idiot. We’ve got shit to do.
The midday sun beats down on us as we step out of the house, its heat already prickling my skin through the oversized hoodie I’ve thrown on to hide my new curves. My sneakers scuff against the driveway as we approach the Mercedes, its silver body gleaming like a polished trophy under the LA sky. Sam doesn’t even pause—he just strides up to it, running a hand over the hood with a casual familiarity that catches me off guard.
“Man, I love this car,” he says, his voice still high and girly from the swap, though it’s laced with that same cocky edge he’s always had. “You’ve had this thing forever. Still jealous you snagged it.”
I stop short, leaning against the driver’s side door, the metal cool against my palm despite the sun. “Actually,” I say, a slow smirk tugging at my lips, “I swapped for it. Took it from some rich dick with five cars he barely touched.”
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