My Stepsister’s Appetite - 01 (Patreon)

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Contains: Breast Expansion as Weight Gain

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My Stepsister’s Appetite

Part 1

I sat in my bedroom holding the white plastic jar of powder in my trembling hand. I’d been watching for the mailman for weeks hoping to catch the package before anyone else in the house saw it. Luckily there was no branding on the small brown box, but it was covered with stamps and stickers in some Eastern European language, and I was glad I caught it before I had to answer any awkward questions.

HungerCup™ the bottle read. A new product by Madsgenix, not yet available in the US. It was supposed to have all the effectiveness of their prescription–only drugs, but available over the counter. When the ad popped up while I was browsing for porn, I couldn’t help myself.

Now I just had to figure out how to get my stepsister to take the stuff.

Hey! Don’t you judge me like that. If you were in my position you’d be tempted too. Obviously I’d never have a shot with a girl like Tabitha. She’s almost as tall as me, blonde and gorgeous. I’ve had blue balls nearly every day since Tabitha’s mom married my dad last year. Her only flaw is her chest. How can a girl that hot have only A–cup boobs? Plus we’re both nearly nineteen now so she’s probably done growing.

Anyway this not–quite–legal food supplement would fix that for her. Maybe she’d thank me. Worst case scenario it might make her eat a lot and gain some weight. Maybe then I’ll be able to stop thinking about her long enough to find a real girlfriend.

Poking my head out of the bedroom, I could hear my stepsister’s voice behind her door. She was on the phone with somebody so I had a window. Quickly and quietly I crept down to the kitchen. Dad was still at work and Sharon — Tabitha’s mom — was outside chatting with our neighbor. I opened cabinets one by one, looking for a way to get my stepsister to take the HungerCup.

The universe smiled on me for once and I spotted a big white jar— the protein powder Tabitha mixed into her smoothies every morning. The jar was only half full so I did some quick math, then measured half a cup of the sketchy drug into the bigger jar. I closed the lid and shook it to mix them together. Now when Tabitha made her morning smoothie, a quarter of the powder would be HungerCup.

I darted back to my room, locking the door behind me to have some ‘alone time’ while I imagined my supermodel stepsister growing big fat tits.

***

Over the next month I paid closer attention to my stepsister’s eating habits while trying not to be obvious. Tabitha was maybe eating more than normal but it was really hard to tell. I read and reread the label on the bottle of HungerCup I kept hidden in my bottom dresser drawer, and as best I could tell from the translate app on my phone, it said the effects might take 4–6 weeks to show. The suspense was killing me.

Then, about a month after I mixed the HC into her protein powder, my stepsister said something that almost made me spit out my food.

“Hey mom?”

“Hmm?”

“Can we go shopping Saturday? I think I need some new bras.”

“Sure we can sweetie.”

I saw my dad meet Sharon’s eyes, but my stepmother only shrugged. My heart was racing. I glanced quickly over at Tabitha’s chest. Her tee shirt was pretty big so I couldn’t be sure, but it might have been a little more snug than normal.

I felt a shift in my jeans so I grabbed my plate and took it to the sink. Mumbling something about job applications I escaped to my room and locked the door.

***

A few more months passed and Tabitha was definitely eating more. I’d often come home from work to find her in the kitchen snacking on chips or cookies, when she used to only eat healthy snacks. She continued to dress pretty conservatively, but every once in awhile I’d catch her in a tank top or something and her tits were definitely growing.

Sometimes if she was staring intently at her phone I’d be able to get a good look at her body. Her tight butt and hips were still at great as ever, but my extensive online research told me she was growing about a full cup size per month.

Near the end of summer I overheard Tabitha in her room talking to her friend Jeanie. Her door wasn’t shut all the way so I stood in the hallway pretending to read something on my phone.

“I love that top Tabby, your boobs look amazing!”

I estimated Tabitha was about an E–cup by now.

“Aww thanks. You know, I think they’ve been growing since like the start of summer.”

“What really? How?”

“Who knows? Maybe some kinda hormone thing.”

“Are you on the pill?”

“Ugh, no! I’m not even dating right now.”

“More guys for me then!”

“You’re such a slut…”

“Anyway I heard that birth control pills make your boobs swell sometimes.”

“Well it’s not that… though I don’t really mind.”

“I wouldn’t either. They look great on your thin frame…”

“Can I feel them?”

I fled into my room and fired up my computer.

***

After finding out my stepsister liked her boobs bigger, I went looking for her protein powder again while she was at work. I knew she’d just bought a new bottle, and I found it barely used. I’d ordered a fresh supply of HC so I dumped almost half of Tabitha’s powder down the sink and emptied the whole bottle of HC into it. If my math was right it should be about double her previous dose.

Tabitha’s appetite went crazy. I’d often catch her coming home from work with fast food bags and extra large sodas. At dinner she ate as much as the rest of us combined. I guess since she wasn’t getting ‘fat fat’ her mom didn’t mind. She was growing faster than ever. All those extra calories had to go somewhere, and they went right into her bra.

About two months after I upped Tabitha’s dose of HC, she started acting kind of strange. I didn’t find out until much later that she’d seen my second shipment of HC in the mailbox. Anyway she started wearing tighter and skimpier clothes just to lounge around the house. I mean, not that it mattered, every shirt she owned was tight now. I knew she was wearing I–cup bras, I’d managed to sneak a peek at the tag on one in the laundry when nobody was home.

“Oh hey, –chomp– you’re home early.”

Tabitha was sitting on the kitchen counter, a package of double–stuff Oreos beside her and a massive glass of milk in her hand.

“Y–yeah, it was slow so I got cut early.” I stammered.

“Nice.”

She wore a black tank top that must have been snug before I started dosing her. Tabitha’s tits were the size of cantelopes and plumped up over her neckline, even a little on the sides! They jiggled every time she moved her arm to grab a cookie from the bag. She was stuffing them in her mouth one after another, pausing only to take big gulps of milk.

I couldn’t stay here in the kitchen and let my stepsister see my quickly forming erection.

“Welp, see you at dinner.” I said as I quickly retreated.

“Kay!”

Another time when our parents were gone, Tabitha knocked on my door. Luckily I was only played a game.

“Come in!”

My stepsister came up to my desk and held out her phone. She bent over so her massive boobs were like a foot away from my face.

“Can you help me with something?”

I helped Tabitha with the frozen app on her phone, sweating and stammering. I was super glad my desk was covering my crotch because I was rock hard within seconds.

“Thanks stepbrother!”

She gave me a quick hug, mashing her half–exposed tits into my shoulder. I stiffened a little and managed to squeak out “sure, no problem.”

After she left I locked the door so I could change my pants and boxers.

***

The next few months were torture. Almost every day I’d run into my stepsister and she’d have some new way to torment me. Little did I know she was doing it on purpose. Any time our parents weren’t around she’d flaunt her growing boobs, or ask me for help, always getting way too close. At dinner she would stuff her face, asking me to pass her more and more food. Sometimes I thought she was looking to see if I was watching her eat.

And her boobs. My god her boobs. They were growing two cup sizes per month now. I hadn’t expected the double dose to be so effective but it really was. Two months after I upped her supply my stepsister was able to rest her tits on the dinner table while she ate. By Thanksgiving she was up to a K–cup, and there were no leftovers. Over Christmas, Sharon and Tabitha made more cookies than we’d ever had before, and I think my stepsister ate eighty percent of them. After New Years her tits were as big as her head, and her mom was constantly telling her to put more clothes on.

My dad and Sharon went out of town for Valentine’s Day, leaving me alone in the house with my stepsister for a whole weekend.

Tabitha knocked on my door.

“Hey, you wanna go get some food?”

“Uh, sure. Where were you thinking?”

“That Chinese place just reopened, I heard it’s good again.”

“The buffet?”

“Yeah!” Tabitha grinned. She held her hands behind her back and rotated her torso, sending her P–cup breasts wobbling back and forth like ocean waves. Their motion lagged seconds behind the rest of her body as she twisted.

“Sure that’s fine.” I stammered. ”Let me get changed.”

“Kay!”

I put on a clean pair of jeans and a nice shirt and walked out to find Tabitha in the kitchen. She was rinsing out a very large glass and the blender in the sink. It seemed weird to me that she’d made a shake or something right before we went out to eat— she usually only made them in the morning. I dwell on it too much though, because I could see the whole outline of her perfect ass through her tight black leggings. She spun around and I saw she wore a pretty top that actually fit quite well. It was snug across her huge boobs but loose and flowing down just past her waist. Having the chance to be seen out in public with such a beauty gave me an unexpected confidence boost.

I drove us to the buffet, and I thought I could hear my stepsister’s stomach grumbling before we even got there. I loaded a plate with a few flavors of chicken and white rice. Tabitha brought back one plate with a mountain of fried rice and another stacked so high with meat and seafood I was surprised nothing spilled off.

Tabitha inhaled both plates before I finished my first, and went up again. I could barely focus on eating my own food with the display going on across the table from me. Her basketball tits rested on the table while she gorged herself on Chinese food.

The third time she went up she seemed to be struggling, but the plates she brought back was just as loaded as the first two trips. Twice more she did this, and I caught glimpses of her stomach bulging into her loose shirt. Tabitha let out a small burp after finishing her fifth obscene helping of food. One small hand reached down to rub her bloated gut.

“–urp– Stepbrother…”

“Hmm?”

“I know about your secret…”

“My… my secret?” I’m pretty sure I felt my heart stop.

“Mmhmm –hic– that special supplement you have hidden in your room… you mixed it into my protein powder, didn’t you?”

My mind reeled as I scrambled for an excuse.

“I… I…”

“It’s okay, I’m not mad.”

“You’re… not?”

“Nope. In fact I chugged four times my normal amount before we left. Would you… get me another plate?”

I was self–conscious about standing up and walking around with the erection I’d been sporting since Tabitha started eating, but I managed to slip it under the band of my boxers before going back to the buffet. Over and over I brought mounded plates back to our table, and Tabitha kept eating, and eating, and eating.

By the time I helped her waddle to the car, my stepsister looked like a pregnant woman about to pop. As I walked her to her bedroom, she stopped at the door, took my hand and placed it on her tummy. It was rock hard, packed tight with a boulder of greasy food. Tabitha guided my hand to press it against one breast. My whole body shuddered as I came, and when my eyes opened I saw my stepsister watching me.

“Oops.” She stuck out her tongue and winked at me.

“Goodnight, stepbrother…”

***

The next morning a loud voice jolted me awake.

“Good morning stepbrother!”

I rubbed the sleep from my eyes to see Tabitha standing in my room in her underwear. Her P–cup bra — her enormous P–cup bra — was hanging on for dear life. She was spilling out of the cups above, below, and even on the sides.

“Look what you made me do to my new bra, stepbrother…”

Tabitha put her arms behind her back and took a deep breath, arching her back and thrusting her enormous breasts forward. I winced as the bra audibly creaked, and then something behind her back popped and tore, and the massive underwear flew right at my face.

By the time I got my stepsister’s bra off me, she was backing out the door, using her hands to cover the nipples on her Q–cup breasts.

“Have a good day at work…”