[Genderswap, Age Progression]

“This has to work. Otherwise, Sis won’t get her body back…”

The boy quietly speaking inside an incredibly dusty room was a boy who had devoted himself to one singular mission. The restoration of his dearest sister, after the experiments that their Father had performed on her. Thanks to those experiments, she was turned into a living doll. A weapon to be used against others. Something that the boy reluctantly did to try and force his way towards a conclusion.

His name was Carl Clover. He had abandoned everything in the pursuit of this goal. Any attempt to grow attached fell flat, all diversions were discarded. None of it was worth anything if he didn’t get to spend them with his sister. And though she was right by his side at all times, in the form of the Nox Nyctores: Nirvana. But she wasn’t herself in this state. She was merely a protective doll manipulated by his abilities. It wasn’t the same thing. It wasn’t even close.

As the young boy looked at the purple humanoid doll, he felt the strings of his heart tug. He had to make sure that this worked. Otherwise, there really would be no other option available to him. There simply weren’t any other ideas that he could muster up, especially after he had done all of this.

The room he was standing inside was a room that belonged to his Father. Countless books, some penned by him, some used by him in his research, were stacked haphazardly all across the floor. Since he had been the one to turn his dear sister into this doll, it stood to reason that there would be to turn her back. As long as he was able to figure out the process.

And while he wasn’t able to do so, there was something that had piqued his interest while he read through all the research. Namely that it was possible to, with enough seithr, create a brand new body for a lost soul. Which meant that if he was able to pull his sister’s soul out of her current body and create one for her, then he would have her standing by his side yet again.

At least, that was the thesis. But to make sure that it worked as he intended, he needed to first create a body to see if he had been theorizing in the correct direction. The last thing he wanted was to make his sister’s situation worse than it already was.

Thankfully, due to all of the experiments that his Father had already done to try and prepare for what he did to his dear sister, there was more than enough seithr in the air. All he needed to do was just make good use of it.

“Just you wait, Sis.” Carl said as he smiled a bit towards the doll that towered over him. “You’ll have a body soon. And everything’ll be back to normal.” He chimed, all while adjusting his hat ever slightly. This was one of the few times in his life where he felt the weight of everything that had happened to his family finally being lifted off his shoulders.

Light started to shine around him, all while Nirvana remained utterly unphased and immobile. Because despite the lingering feelings that rubbed off her soul and into the doll, she wasn’t able to do much without a direct command from Carl. And as long as Carl was occupied with this ritual… Then she wouldn’t be able to do anything.

At least, that’s what he thought. But as the seithr in the air started to become visible, the softest and gentlest blue glow started to pour from her eyes. And it almost seemed as if she was becoming conscious. That’s the only way he could explain the glow that was resonating off her body.

“It’s… It’s working!” Carl cried out, his eyes lighting up. He was going to have his sister back. He was going to be reunited with the one that had protected him and loved him… He was going to undo everything awful that his Father had done to the two of them, and then he was going to…

His thought suddenly grinded to a halt as he realized something. Sure, her soul was being roused from within the doll that served as her prison. But the ritual that he was going through… It didn’t seem to be creating a proper body for her to inhabit. Where was the new body that he had hypothesized? Surely all of this seithr wasn’t just going to swirl around without doing anything..?

As Carl let his thoughts drift through and tried to understand what was happening, he neglected to notice the fact that more than a little bit of the seithr in the air was starting to cling to him. And if there was one thing that seithr was good at, it was contaminating the things that it made contact with.

Slowly but surely, the light that had been filling the room, the same light that had been filling up the eyes of the doll that contained his sister’s soul… That very same light was covering Carl from head to toe. Covering him to the point where it was almost impossible to discern his figure, much less his features.

Only then did he realize that something was wrong. And the way he reacted was with a powerful gasp and a sharp inhalation, serving to fill his body with even more of the seithr. Causing him to collapse as his body trembled harder and harder.

“W-What’s going on?” Carl muttered, his grasp on the situation quickly loosening as he felt his voice heightening a few octaves. All while his hair was growing to the point where he could barely see anything.

It wasn’t just his hair that was growing either. His body felt incredibly cramped inside his current outfit, to the point where he wanted to just try and tear it off and get some sort of breathing room in the process. But if he did that, then-

He didn’t get much of a choice. Just as quickly as the thought had drifted past his mind, Nirvana activated. And using her incredibly sharp fingers, she carved the clothes that covered his body until there was nothing left. Not even a single shred remained, leaving her younger brother completely uncovered and exposed to the elements around him.

Even his glasses weren’t safe, though he found that he didn’t need them. Because his vision was clearer than ever, prompting him to move a bit of his hair out of the way to look at his hands. And almost immediately as he had done so, he wished that he hadn’t. Because his hands were more feminine than ever before, to the point where they looked like they belonged on a much gentler soul. Like either his mother or his sister.

Taking a brief look down at the rest of his body, he noticed just how feminine he looped. Smooth hips, smooth skin, slender curves… He looked like a girl. But he couldn’t be one, he was sure that he wasn’t. That, and he didn’t have any elements that would make it easy to identify him as one.

Maybe he shouldn’t have thought about that. Because not even a second passed after the thought left his mind before his chest started to ache. And a simple rub to make sure that nothing was broken was all that it took to trigger the rest of the necessary changes, as his bosom started to swell and grow nice and heavy.

Carl moaned and panted as he felt his breasts growing. Not to the point where he looked absurd or anything, but just big enough that it was even harder to think of him as a boy. Though, upon examining them and feeling their weight in the palms of his hand, as well as how it made him feel when he touched them… It reminded him of his sister. More so than he would’ve expected.

Was he… There was no other explanation. He was turning into his sister’s old self. Or rather, his body was taking on her old appearance. A girl who had been forced to mature too early to make sure that she could take care of her younger brother. Something that was only emphasized as his thighs started to widen a bit more.

If this was really true, and he was turning into Ada, his dearest sister… Then what was he going to do with her soul? She couldn’t just live inside him, then all of this would’ve still been for naught. But at the same time, if he could replicate what he had done, then…

His thoughts about continuing this experiment were cut short by the sudden sharp spike of pleasure down below. And as he reached down to try and touch himself to ensure that nothing had gone wrong, all that he felt was a wet hole. Just that, and nothing else. Especially not a set of testicles or a phallus.

His manhood had disappeared. And his sister’s womanhood had taken its place. Which really meant that he couldn’t call himself a he any longer. Carl was now stuck in the body of his dearest sister, Ada, leaving his experiment as a failure and leaving him no closer to solving the issue of rescuing her from the body she was stuck in.

“Sis…” Carl muttered as she looked at herself in a nearby mirror, coming face to face with the truth. Even their faces were identical at this point. Just looking at her face reflected in the mirror was enough to trigger happy memories of a time long gone… And at the same time, caused her to blush as she realized just how sensual her sister’s body was, now that she was up close and personal with it…

….W-What was she going to do now? In a way, she had her sister back. Not in the way she preferred it, but at the same time, it would be a shame if she didn’t… Well, try out her sister’s body in some way. Especially since, after everything was said and done, she was older now, wasn’t she?

As she slowly let her eyes drift down her body, she noticed something out of the corner of her eye… Namely the fact that Nirvana had disappeared. And immediately, her heart skipped a beat as her mind started to race and imagine the worst possible situation. Could her sister’s soul have managed to escape the doll’s body, and now it was inside her? Did it disappear? Was she now stuck without her sister, and she’d have to be alone with only this body as her single memento?

Thankfully, before Carl started to spiral too far out of control while kneeling down on the floor, Nirvana made her return. By opening both doors rather violently, all while carrying a familiar looking dress on her shoulder. It seemed that she had some amount of autonomy at least, which made it clear that Ada’s soul was still inside her.

But that dress. It was familiar. Too familiar. And as it was lowered off the doll’s shoulder and held in front of the newly transformed girl, she couldn’t help but blush a bit more as she realized what it was.

It was one of her sister’s favorite dresses. She was honestly shocked to realize that her Father had kept a spare set around here. And if she did wear it, the line between her and her sister would blur even harder. But at the same time, Nir- Ada wanted her to wear it. There was no other explanation.

Carl took the dress and slipped it on. It wasn’t much, a simple black dress with elegant stripes that reached all the way down to her ankles. But it really emphasized what a gentle soul her sister was. Even just looking at her trying to take on the same vibe was enough to make a tear roll down her cheek.

“Sis…” Carl muttered, as he looked to Nirvana with renewed vigor in his eyes. “We’ll figure it out. We’ll find you a new body. I promise.” Even with this setback, he was determined to make it up to her. One way or another.

And the soul inside the doll made the doll nod. Though they were still ‘apart’, they had grown a bit closer thanks to this experiment. And there was only one thing left on Carl’s mind, besides his pursuit of his sister’s freedom.

...How exactly did the female body work..?