Lindsay gave another shudder, and an almost comical grinding sound arose as her diminutive toddler body began to stretch.
Her back arched as she grew into the body and form of a young girl, her arms lengthening with her legs, her body growing older by the second.
She gasped, flexing her short arms, feeling slightly nauseous as she grew nearly a foot right before her sister's eyes.
"AH!" she gasped, rubbing her chest through the tight clothing, her still childish body overfilling the seams.
She smoothly transformed from a little girl into an older girl, her familiar features appearing as her freckled face stretched out, her eyes brighter by the moment.
The twine that had been used to hold up her formerly oversized clothes snapped, allowing the clothing to fall down to above her extending wrists and ankles.
Her no-longer pudgy hands opened, and Ali watched her sister's fingers lengthen, growing longer and more slender, her stubby fingernails growing almost sharp.
She watched her toes emerge through the breaking shoes as her body became more mature, still dainty feet on a fast growing 9-year-old.
Now Lindsay was Ali's height again. The sisters gazed at each other uncertainly.
Five feet she must have measured now, growing up within a single minute.
Her trembling growth slowed and stopped briefly, halting as she bent over and clenched her hands, squeezing her eyes tight, and then she shuddered again, and again began to grow.
Ali thought she could actually see the bones pushing outward within the confines of her sister's body, compressed against her clothing, an odd gyration as her body thickened with age.
Her growth sped up for the last time, her back widening through loudly separating layers of cloth, before she again pulled back, arching her spine again in the other direction and opening her mouth to suck in a deep breath of air.
Teeth glimmered briefly as her body tore the last seams of her much too short clothes, her thighs thickening dramatically along with her upper arms.
Despite the fact that she only appeared to have the body of a 13-year-old, that body was already big enough to break all her toddler clothes. Her ribcage barreled with each breath, her legs swelling outward at the calves and the thighs.
She rubbed her chest as her mammaries thickened, the breasts bulging separately with each heartbeat. With a loud snap the remaining piece of twine around her middle broke away.
Then with another pause, a shudder, Lindsay's growth slowed as she swelled into full womanhood. Her almost completely naked form grew rounder and tighter, though one freckled breast was partially flattened by a strip of torn undershirt until the fabric burst away, and the big breast jiggled free.
Ali looked up as Lindsay's height now far exceeded her own, the uneven shreds of her disintegrating shirt long untucked from pants that were more holes than fabric, and the remaining cuffs of the pants and the shirt creeping higher up her arms and legs.
She watched Lindsay's pubic hair sprout as if it was being airbrushed on. Now subtle crunches and grindings came to her ears, that of bones and tendons creaking, and in short order her coltish, relatively slender form mutated into an hourglass shape as her hips swelled outward, causing the last shreds of her pants to fly both ways. Her large bosom barreled outward and her middle compressed somewhat, though her stomach was not as flat as it used to be.
Lindsay took a confused step toward Ali as she rolled her hips forward, her now mature form tightening as the remnants of the shredded pants legs hit the floor. Small checkered pieces of her shirt still clung to her body. Her slightly pot-bellied stomach pushed outward underneath, complete with an outie belly button; her long fingers rubbed it. And then the pot-belly of adolescence flattened somewhat as her body grew a few millimeters wider.
There was a new snapping sound then, and Ali's gaze lifted to Lindsay's face as she raised her hands to remove the hat whose brim had just popped open, the hat that had remained there as she had aged; she took it off to shake free a mane of red-brown hair.
Then she smiled, her full lips moistened as she lowered the hat and lightly caressed it against her chest. She sighed then, looking down at the full chest that hung over her beautiful teen stomach.

Suddenly another snap greeted their ears, and with a shock Ali viewed the waistband of her own trousers popping under the pressure of lightning growth, the zipper tearing apart to reveal her white panties.
Now Ali watched her own shirt draw tighter, her thin legs beginning to fray the inseams of her pants, and as she watched, the seams along the insides of her legs popped open in several locations, the tears rapidly widening. Her trembling thighs pressed together as she stood up straight then, higher than she should have been capable of.
As she stared higher, the front of her chest began to bulge. Twin buds began to swell, thickening moment by moment, growing larger by the second.
They rapidly pressed against one another, firming up, rising high atop her chest, the shirt groaning as it bulged tighter than she had imagined possible. Her nipples likewise erected, growing diamond hard and throbbing painfully on her generous breasts. She saw her own pubic hair come in over the panties, darker than her sister's.
She heard and felt her telescoping legs tear easily though her pants, separating them into strips that fell in tatters to the ground about her now bare feet, her shoes forgotten strips of leather. She watched the remaining pieces of her pants slide down her legs.
To her surprise her shirt suddenly exploded off her unnaturally aged body, a few of the pieces briefly draping around her waist, and she found herself as topless as her older sister.
Damn she would be TALL when she grew up. Her naked thighs pressed hard against one another, continuing to widen as they grew longer, increasing her height until she surpassed Lindsay again by four inches, though she didn't think her slender form would be as heavy.
The naked women faced each other.