Sam a 10 year boy notices his 7 year old sister Samantha moan. She starts to strip. First she takes off her shirt, then off comes her skirt and panties. As she finally strips she lets out a load moan and Sam notices that she is shaking. Samantha starts to grow taller. 3 feet! 4 feet! 5 feet! After five feet she stops growing and Sam notices she has a body of a 16 year old without any breasts, hips, waist, arched back, and other mature features. Sam hears a sucking sound coming from Samantha's vagina. She moans even louder and Sam notices the vagina separating, revealing her labia, clitoris, and other vaginal parts. Sam notices that Samantha's back arches drastically, and with a loud snap and she now has a very curved back. Her butt starts to grow getting bigger and bigger. Sam starts to strip and starts groping Samantha's new butt. It's soft and not too firm then Sam notices Samantha's waist thin and Sam hears popping and Samantha's hips widen. "That leaves the breasts," Sam thinks and he notices that Samantha's nipples start to harden and grow longer permanently stiffing. Her areola starts to widen to a 2 cm diameter and both her nipples and areola darken. Her breasts start to grow in a triangular fashion leaving two small breast buds that Sam start to grope. Samantha moans even louder and her breast start growing from buds to an a cup not stopping growing past a b cup onto a c cup. The growth fills Sam's hands and he gropes more furiously gaining pleasure in this. Samantha's breasts now are d no dd cups stopping their growth there. Sam starts to feel a tingly feeling and grows to Samantha's size. His penis starts to ejaculate and shrink with immense pleasure. As it shrinks his balls receded and he is left with no genitalia and a prostate which flattens to become a uterus. A ripping sound is heard and Sam gains a vagina becoming Samantha just like her sister. Samantha doesn't notice the changes occurring as her hips widen, butt grows, back arches, waist thins, and her breasts which have become buds but the nipples and areola haven't matured yet. Her breasts are now a dd cup as the areola widens and darkens and her nipple stiffen and grow. Samantha- the one being groped- turns and notices that a duplicate of her has appeared and starts groping her furiously as well. Both girls' skin lighten to a pale white and their hair becomes black. Two bras and panties appear on them. As they stop groping they notice that they have been fully clothed with micro skirts and a skin tight, black, and strapless v neck to match the micro skirt. Then out of nowhere both girl start to moan and fall over skirts flaring and panties showing. Both girls start to grow the mini skirt gets smaller and their panties start to show. Both panties got tighter and you can clearly make out the shape of their vaginas both between their legs and the clit in front. Their shirts start to rip revealing massive cleavage and their bras getting tighter as their under breasts spill out the remains of their micro skirts and shirts fall off. Their bras snap under the massive pressure of growth and the panties mercifully snap under stress. Naked again the two girls shrink and Samantha- the previously known Sam- starts to feel weird. She starts to lose height and seems to get younger same happens to Samantha. Both lose their hip sizes and their backs straighten. Their butts shrink and their waists widen their areolas and nipples lighten and shrink their nipples flatten as they lose breast mass. A tingling occurs and causes orgasms in them as two penis flare out as well as two pairs of testicles. Their vaginas close and prostates form. Sam- original gender now- starts to get more muscular and his penis grows and gets thicker. Sam-new gender- starts to change as well, he starts to become a girl again. His back arches and butt expands getting as big a dd breasts his waist thins and breasts grow to e cups with 4 cm wide areolas and 3 cm tall and 1 cm wide nipples he shrinks to a height of 4' 11 and a body of a Japanese maiden. His hips widen to a huge width and is now getting pulses in his penis and testicles as the shrink to nothingness and his dick shrinks as well. Now with her new vagina Sam starts to grope her and starts to insert his penis into her tiny vagina. She moans as it finally inserts and is going in and out. Sam ejaculates and starts to merge into Samantha. Samantha having fully absorbed Sam starts to change. She gets taller and her breasts shrink to dd and her waist and hips slightly widen and shrink respectively. Her butt shrinks to a c cup breast size. She finds a tiny black thong and bra, a white micro skirt and strapless white v shirt. She puts them on and after she finishes and orgasm occurs and her shirt and micro shirt get ripped off in intense pleasure. She writhes so much that her bra and panties snap and now she returns to consciousness as a shapely 16 year old girl and now explores her body. She gropes her breasts and butt. She notices her mature vagina and masturbates and her nipples stiffen in excitement and she finally faints from pleasure to wake up as the 16 year old to stay that age forever.