Jeff thought of his older sister Hilda, it would be really strange to turn into her living pussy but that just excited him even more.
Speaking of the devil, Hilda showed up in his room not even knocking the door. "Hi little bro, how is it going?" She approached him even further. "Playing some of your weird games on your PC?" She giggled.
Jeff and Hilda had a big level of confidence on each other, they had a small talk about the computer, at first Hilda didn't believe him so much but he just gave a few details more and Hilda's interest began to grow, being interested on the transformation part.
"Wow! So you were using it? What transformation are you testing now?"
"Well..."
"I'm open to everything Jeffy, how bad could it be?"
Jeff sighed and tried to explain every detail of the Chronivac to her and its capabilities. "So yeah, it can do pretty much everything and for fun I set it to be able to turn into someone's human body part, well... Specifically their vagina"
"Then... Were you planning to become my vagina?"
"Human vagina but... yes... I'll be more like my own face in your crotch but functioning as your pussy..." He blushed.
Hilda thought about it for some seconds, she noticed how Jeff looked worried after his answer, but she actually was interested on his proposal. "I see no problem in that, it'll be a nice and exciting way to be closer for a while~"
Jeff recovered his excitement again. He explained some parts of the process to her, requiring Hilda to remove her lower clothes to make Jeff start his transformation.
Hilda removed her pants and panties revealing her slightly hairy vagina to her little brother without shame. "Like this?" She said in a sensual tone.
"Yup! Now we can begin"
Hilda spread her legs facing her crotch to Jeff's feet, Jeff laying face down shoved his feet inside her sister's pussy, they couldn't normally fit but due the Chronivac's power he could easily enter like it was an slimy and tight bag of flesh. The rest of his body was quickly sucked by Hilda's vagina until only his face was outside, during the process Hilda's reproductive system disappeared, uterus, ovaries, everything, with Jeff filling all the emptiness, even her vaginal lips, clit and pubic hairs were erased, now it wasn't a vagina anymore but more like a hole between Hilda's legs showing her brother's face. Jeff joyfully squirmed with almost all his body inside her.
"Oh god" Hilda left out a little moan before Jeff fully entered. "This... feels kinda weird" she rubbed her belly, even that outside she looked normal she could feel the entirety of Jeff filling her. "Are you supposed to be my pussy now?"
"Nope, I'm still a normal person inside you."
"I think I get it, I don't feel horny or excited, this thing got rid of my clit! Is that all?"
"Don't worry" Jeff giggled. "Now I'll turn into a real human pussy!"
Jeff's body started to internally change ready to fill the spaces left inside Hilda, Jeff's legs began to shrink until he was a mere torso with only his head attached. Jeff's face and Hilda's body looked normal from the outside but the whole process was happening inside. Then Jeff's internal structure began to merge with Hilda's insides, his whole organs began to reshape themselves, his throat turned into a vaginal track leading to his stomach, which was transformed into Hilda's womb, therefore a cervix formed in the womb's entrance. Next his lungs fused into a single fleshy recipient that would eventually be the bladder but was just connected to Jeff's mouth instead of both his nose and mouth, another but smaller hole formed inside his mouth that resulted into the urethra. His nose nervous connections morphed to give pleasure to Hilda, so his nose turned functionally into her clit. The rest of his organs disappeared turning into flesh filling the rest of Hilda's emptiness, Jeff could still be alive thanks to the Chronivac and getting all he needed to live from his big sis. The only remaining thing was Jeff's penis which immediately shrunk until it disappeared, while his ballsack separated and stretched, each one in opposite directions, at the end his testicles changed its shape to turn into ovaries, which now were connected to Hilda's womb, formerly Jeff's stomach. Jeff was finally a human vagina.
During the said process Hilda felt her insides twisting, assimilating and filling with Jeff, at the end she just felt some waves of pleasure coming from her crotch. "Oh god you feel amazing, more than my original pussy even that despite you look like your normal face between my legs! We have to test this little bro~" she quietly moaned rubbing her brother's nose for a couple of seconds, it felt dozens of times better than her previous clit, Jeff's mouth got a little wet in the moment.
"I told you! now you can play with me as many times you want!" Jeff kept drooling Hilda's fluids from his mouth.
"Of course I will! And just to know, how long will this thing last?"
"One week, so we have plenty of time. Also this whole thing will be unusual just for us, everyone else will think that this is normal"
"Sounds good! And I know what to..." Hilda said feeling a pressure in her lower parts, Jeff could feel it too, he needed to empty his, well, THEIR bladder full of pee. Hilda rushed to the bathroom sitting on the toilet, "I hope this isn't so bad for you Jeffy" she said leaving the rest of the work to her vagina brother, he opened his mouth and let the stream of be expelled from his other and little mouth hole. After being done with her pee, Hilda cleaned Jeff's mouth with the toilet paper.
"Well, that wasn't so bad, maybe the Chronivac changed my taste, not that I'm complaining" He said kicking his lips.
"I'm glad this is enjoyable for you as much as it is for me!" Hilda left the bathroom. "Now, as I was trying to say, I know what we're going to do now~"