You woke up the next morning, feeling like yesterday had been a strange dream. But you knew in your heart that it had not been and Molly was indeed growing bigger and had an appetite for more.

You checked your phone and saw a text from your mom:

Going to spend a few more days here, having fun catching up with old friends. Hope you and Molly are doing good xoxo

Great. Possibly the only person who could get Molly to stop taking the GrowTech pills was not going to be home. By then, it might be too late to do anything about it. You had to find a way to send your mom a picture of Molly because she wouldn't believe your story without photo evidence. You got out of bed and saw that her door was closed. The food you'd brought her last night had all been eaten and you knocked on the door, anticipating Molly's new size. There was no response.

"Molly, you in there?" you whispered. You opened the door a crack.

Her room had a strange odor to it. The air was heavy and smelled like a mixture of sweat and something else. You walked in and couldnt find Molly anywhere. Her clothes were strewn across the floor and you gulped seeing the tank top she'd had on last night. It had been ripped down the middle.

There were also a few bras on the ground which you assumed to be your mom's, since they certainly weren't Molly's. A thought occurred to you - this might be your chance to steal back the GrowTech pills!

The question was, where was Molly hiding them? You opened her drawers, one by one, searching. In her underwear drawer you saw panties which would now be painfully small on her. You also found a small vibrator which you dropped in disgust as soon as you realized what it was.

You were about to give up when you checked under the pillows -- there they were! The two GrowTech pill bottles! You grabbed them and turned around, planning to take them far away from Molly and throw them deep in the woods somewhere. As you turned though, you felt an uneasy sensation.

Your eyes were bombarded with a massive pair of boobs stuffed into a bra that was too small. You lifted your gaze upwards, until your eyes met Molly's pair of bright green eyes.

"Hiya Timmy! Like the new me?"

"M-M-Molly..." you stammered. You stepped back and looked her up and down. She was only wearing that tight bra and a pair of black lace panties, which hugged her curves. She was barefoot and you noticed how big her feet had grown.

Molly stepped towards you and pinned you against the wall. Her breath was hot as she spoke,

"I told you you wouldn't be the biggest for long. Now I'm the BIG sister. Hahaha."

You couldn't help stare at her boobs which were practically being pressed in your face.

"How tall are you? I mean what the fuck, this is unreal!"

"I know, this is better than I could have ever imagined! I just measured myself, I'm about 6'4''. Another half foot! Can you believe it? And I'm sure you noticed these puppies," she said, hefting her breasts. "I had to dig out one of Mom's old maternity bras, it's an E cup and as you can see a little  small for me. Guess I'll have to go bra shopping soon. I could use some new lingerie too, her panties are a little tight on me."

Molly turned around and wiggled her butt. It was huge now, and it turned your mom's underwear into a thong. You were transfixed on her ass cheeks which jiggled hypnotically. She peered over her shoulder and caught you staring.

"Something you like? You know, I'm beginning to develop certain needs at this size and you could help me with them..."

"Needs?"

"Yes. It seems like one of the side effects is an increased appetite. And I'm not talking about food. I've never felt this horny before and, well, you're not such a bad looking guy."

"Molly, I'm your brother! That's disgusting."

"I've seen the way you look at me. The way you look at these." She stuck her chest out.

"Still. That's gross. Why don't you go sleep with some guy from school, why me?"

"You're my brother Tim. I feel like I should take care of you."

"Take care of me by grabbing my dick and threatening me if I don't do what you want?"

"I'm sorry about our little altercation last night. We were having a power struggle. It seems I've won," said Molly. "Yes, I want your obedience. And in return, I'll take care of you. It's not such a bad life having a bombshell of a sister, you know."

You thought about this. You were enjoying this gentler side to Molly and wondered if it was real or just a ruse so she could live out her perverted fantasy of sleeping with you.Was any of this real? Was she tricking you to see your reaction?

You looked at Molly's face. Strangely enough, though her features had grown bigger, she also seemed more beautiful. Her eyes were just as they'd always been, but she had lost some of her baby fat and her lips seemed fuller. You really wanted to kiss, her, but she was your sister.

As if she read your mind, Molly said:

"There's nothing wrong about wanting what we want. Society just tells us it's wrong. We're both adults, Tim."

You stared at her cleavage, imagining what was underneath her bra.

"Before we can do anything, though, I believe you have something of mine," she said.

Suddenly, you remembered the pill bottles that were in your pocket. She must have noticed! You had a choice here: give her the pills and allow her to continue her growth or refuse and suffer the potential consequences. At her current size, you still had a chance of beating her in a fight. All it took was a picture to Mom and Dad and she was finished. You made up your mind and took out your phone.

"What are you doing?"

"Stand still." You snapped a photo and started to text it, but Molly grabbed your phone out of your hands and held it out of your reach.

"Give it back!"

"No. You've been naughty, trying to get your sister in trouble. Now, this phone belongs to me."

You jumped to try and grab it, but it was futile. You bumped into Molly's boobs and fell backwards, which made her laugh hysterically.

"Looks like your 'little' sister is too much for you to handle!"

You scowled at her. She bent down over you and kissed your forehead. For a moment you were too stunned to move and then you felt her hand in your pocket. You anticipated her giving you  a handjob or something but instead she pulled out the pill bottles. She shoved one down her panties and the other in her bra.

"I'll be in the hot tub. Why don't you join me and we can see how much fun these little pills let us have?"

She strode off, her ass bouncing with each step. Now you had no phone and no pill bottles. Now you were Molly's. But was that really so bad?

-----------

Not wanting to displease your newly bigger sister, you put on a swimsuit and went down to the hot tub on the back porch. Molly was already there, with only her head sticking out of the water.

"Oh good,  you decided to join me. I was worried I'd been a little too forward earlier."

"Some time in the hot tub might feel nice," you said. "It's been a crazy weekend."

"Mmm I know. Things will never be the same again."

You climbed in, sitting across from your sister. Her legs stretched across the whole tub and she had to bend them to fit properly. You glanced down to see what she was wearing and saw it was a tight read bikini, probably one of mom's, that barely contained her amplified assets.

"Something you want to see, lil bro?" Molly smirked.

"Uhh..." you thought about pretending you weren't turned on but figured she'd see right through your lies. "Yeah. I wanna see your boobs."

Molly laughed and looked impressed with you.

"Finally! That's what I like to hear from you, mister! You'll get a chance to see them in all their glory, but first I want to have a little fun with you. Come over here."

You obeyed and slid over to Molly's side of the tub. She seemed so big compared to you even though she was just a few inches taller now. She grabbed you and placed you on her lap with ease. That was a little weird. She wrapped her arms around you and cooed in your ears,

"How does this feel, Tim? Do you like having your big sexy sister take care of you?"

Your boner told Molly everything she needed to know. She put a hand on it and began to stroke.

"Molly..."

"Shhh.... let me take care of you like a good big sis."

She kept stroking your cock and playing with your balls until she sensed you were close to cumming. Then she pushed you off of her and suddenly stood up. She seemed to rise endlessly, water coming off her body and dripping from every delicious curve she possessed. Her tits were pushing her bikini to its limits and her womanly hips sucked in her bikini bottom, making it no more than a cover for her pussy and ass crack.

You stared at her in awe, with your raging hard on, feeling blueballed.

"Keep touching yourself," she commanded. "Stroke your big hard dick for Molly. Mmmmm that's it, Timmy. Pleasure yourself thinking about me.... thinking about THESE"

she flung off her bikini top and her massive tits bounced free. They were perfectly round and had a nice perkiness to them that only young breasts do. Her nipples were erect and proudly displayed as Molly shook her chest, making the flesh jiggle for your entertainment. You couldn't contain yourself anymore and had a massive cumshot, probably the biggest of your life. Molly grinned when she saw this and knew that her power over you was absolute.

"Good boy..." she purred. "Now. I'm going to go and do a little growing and invite some friends over. I'll visit you in your room later tonight. Until then, I don't want a peep out of you, got that?"

You nodded. She bent over, her boobs in your face and her mouth just above your eyes.

"Good. Love you bro!!"