[Incest, Breeding, Jinko TF]

"One more time, Gaoko-nee!"

"Don't push yourself too hard, Tai. I wouldn't want to see you burn out."

"But I want to protect you too, Gaoko-nee! It's not fair that you do all the work!"

"It might not be fair, but if you got hurt, who would I have to protect?"

Two siblings were in the middle of a spirited argument. A simple disagreement between them, especially since both were unwilling to move from their respective viewpoint. It was beyond easy to see them as siblings due to their shared stubborn nature.

The young boy, who barely reached up to his dear sister's stomach, was named Tai. And after their parents had disappeared and left him all alone with his sister, he desperately wanted to prove that he could protect her too. Even after she had ended up transformed into a Jinko, he still wanted to do what he could. Not because he wanted to prove anything, just because he wanted to protect her.

His sister, Gaoko, was once a normal girl. But due to the nature of protecting a young boy and the fact that this world of theirs was slowly being corrupted thanks to the presence of Monster Girls, she had been on the verge of falling victim to those corruptive effects. But thanks to a potion from a certain sneaky merchant and the love from her brother, she had transformed into a Jinko and retained complete control over herself in the process. Granted, she still had to deal with the kinds of needs that a Monster Girl had, and she constantly had to deal with the instincts that came with the specific transformation... But thanks to her love for her dear younger brother, those problems were practically nonexistent.

"If you keep protecting me without letting me grow strong, then I can't protect our family once it grows bigger. You're just one girl, Gaoko-nee!" Tai shouted, all while dramatically pointing at his older sister's belly. A belly that was both ever slightly toned to show how strong she was, as well as bulging out due to the life that was growing within. After all, the act of loving one's little brother took a toll on her womb...

Gaoko blushed slightly as he went straight for her proverbial weak spot, before sighing a little. She couldn't really argue against that either, because he was right. She was just one girl. And this entire transformation was one she had brought on partly due to the corruption of the land, as well as the need to keep him safe. Teaching him to fight and helping him grow stronger, especially to help make their family stay safe... It was the simplest road forward.

"Still." But she had to act like the adult in the relationship. "That doesn't mean that you can push yourself until you end up breaking something. We're ending our training for the day, and that's final." Gaoko said, putting an end to their bout as she crossed her arms. She wouldn't fight. Not for a second longer. And if she didn't fight, he couldn't grow stronger.

On any other day, Tai would accept his older sister's decision. But as he looked at her with those crossed arms, it was like something started to roar inside him. He couldn't accept that she wouldn't fight him, panting and gasping as he clenched his fists. "One more time..!" He cried out, even as it seemed like he was far too exhausted to fight.

"Tai..." Gaoko muttered, only for her eyes to widen as she picked up on the subtle tells in the boy's stance. Something was bothering him way more than frustration from a loss. "Tai! Don't!" She shouted, as she quickly assumed a defensive stance. She had to prepare herself, otherwise the boy would hurt himself.

He didn't listen. With a wild roar, he lunged forward and tried to actively slash her instead of punching her. And in that split second, his nails grew thick and long as he tried to prove that he was strong. Not that it was the smartest way to fight, it was just wild and vicious... And ultimately showed that the corruption of the land had started to get to him.

Which was why his slash didn't meet its mark, instead being stopped midway by the older girl's hand firmly grasping his wrist and throwing him to the ground, mounting him just to make sure that he didn't get any funny ideas.

"Let go! Grrrr!" He growled and he hissed like an overgrown cat, unaware of the beastly look in his eyes. He saw an enemy, and he wanted to strike. All while the feeling inside him grew stronger, the howl and the roar forcing the beastly boy to go on the offensive. Even if he was stuck underneath his precious sister.

There was only one thing that Gaoko could do to calm him down. And that was simply to capture his head in between her thighs. Press down on him to make sure that he couldn't move and couldn't breathe. Just to make sure that he calmed down. "Open your eyes, Tai!" She shouted, making sure that her muscled thighs did what they were meant to...

Tai trembled and gasped and panted, especially as he felt his head pressed in between those mighty thighs. He tried to struggle free, right up until it felt like he was about to pass out. It was then that he was forced to roar, as the feeling inside him reached its peak. A peak that made his body glow with some sort of primal energy...

Gaoko recognized the energy. It was... Well, okay, she couldn't really explain it. But she knew that it was the same kind of energy that had turned her into a Jinko. Which meant that by fighting him, she had somehow infected him and forced him to transform into a Monster as well. But at least he wasn't turning into a girl, she could tell that much based on the lack of growth near his chest.

She climbed off her little brother so he could actually breathe, and in the process the transformation that poured through him sped up. The glow consuming more and more of him, as his silhouette... started to shrink? He wasn't growing younger, she could definitely tell that. It was more like he was being forced into a more compact form, one that made him look like a cub when compared to her...

Indeed, as the glow vanished, it was clear that Tai had found a way to become adorably small. All while the subtlest traces of muscle forced its way across his body. But it was also clear that he was no longer human. Whether it was because of his paws or his claws, or the fur that kept him nice and comfortably warm, or the adorable ears on top of his head. He was a Jinko, just like her... Or, well, as close to a male specimen of the species as he could possibly be. It wasn't very often that a male was able to transform like this, after all.

Tai gasped and panted as he slowly got control of himself. He was hot. He was really, really hot. And not in the attractive kind of way. In the way where he felt like he was about to overheat if he didn't do something about it. "W-Water, water!" He cried out, desperately reaching for something to calm him down, lest he end up burning alive from the inside.

Thankfully, Gaoko had thought ahead. And as soon as he started to cry out in desperation for something to cool him down, she ended up dumping a bucket's worth of water straight onto his head, to ensure that he got all the cooling that he needed. Even if it did end up puffing up his fur and making him look absolutely ridiculous in the process once he started shaking off all the water.

"Haaah... Haaahhh..." Tai kept on gasping as the heat slowly started to die down, even if it took a good amount of time before he felt like he was actually able to just stand there and think straight. The feeling inside him that had forced him to transform died down, and he was left to slowly realize what had happened. Not that he immediately looked at himself. Instead, his gaze was locked entirely on Gaoko, and her beautiful and toned body...

The tiger boy let out a mild yelp as his erection caught him completely off guard, his libido having hit brand new peaks thanks to his transformation. And his shaft was... Well, to say that it was impressive for a boy his age would be an understatement. Just the sight of it was enough to make Gaoko wet down below, and when it would've taken several seconds for her body to heat up after catching a glimpse of his rod when he was still a human. It seemed as if they were extremely compatible, if one were to take this as a sign...

"How are you feeling, Tai?" Gaoko was doing her best to suppress her instinct. She needed to make sure that the boy was capable before she'd try anything. As much as she just wanted to ravish him and make sure that he filled her just as he had done when she transformed the first time around.

Tai finally caught his breath as his elder sister showed concern for him, prompting him to look down at himself. "I feel... Really, really warm, and..." He paused as he also realized that he had managed to shrink, prompting him to pout and sigh. "Why am I even smaller!? You grew bigger when you became a Jinko, how come I'm small?!"

Yep. That sure was her dear little brother. Even if he had grown smaller, even if he had been transformed into something close to a Jinko, he was still her beloved little brother. And she wouldn't want him any other way. Ah, how utterly adorable...

She didn't even bother trying to answer his question, as much as she just grabbed ahold of him and hugged him nice and tightly. All so she could keep him as close as possible. All so she could make sure that he wouldn't get away from her. Even his scent was perfect, to the point where she couldn't stop her lower lips from drooling in response to his natural pheromones. Oh, she definitely needed to drain him dry...

"Gaoko-nee, you don't have to hug me that tight..!" Tai cried out, trying to free himself from her arms due to how tight she was hugging him. And it was actually not as difficult as she would've originally thought, all thanks to his transformation imbuing him with quite a fair amount of strength. Which meant that he was actually able to break free, albeit not without leaving him winded once he stepped away from her a bit.

He looked at his claws in surprise, before looking back at Gaoko and noticing how aroused she had gotten. The sight of which made the blood in him rush down to his own rod, which in turn made it rather difficult to focus. Oh, why did his sister have to be so hot? ...Not that he was actually complaining, he wouldn't even think to genuinely complain about how attractive she was. He loved her, after all.

Gaoko slowly drooled from her mouth as well as her pussy as she took a single step towards him. "Tai... Tai..! TAI!" She shouted as she pounced on top of him, unable to constrain herself any further. She wanted to breed with him! She wanted him to fill her, and there was nothing that was going to stop her!

Tai met her pounce the best he could, but he couldn't force her back before she ended up slamming him down against the ground. And as a result, he was forced to penetrate her almost immediately afterward, his cock slipped straight in between those slick lips as he let out a powerful moan...

Of course he wasn't the only one that started to moan. She was more than willing to let her arousal echo out. Especially since the feeling bubbling inside her when she looked at him wasn't just arousal. It was proper heat. Seeing him made her interpret the young tiger as her mate... And unfortunately for both of them, it just happened to be mating season.

As Gaoko kept him pinned to the ground, Tai was forced to accept her constant bouncing. She was violently trying to milk his cock, trying to satisfy the heat inside her. And while it certainly helped the heat inside him, he wanted to thrust as well. The heat inside him told him to breed his mate, and the fact that she was taking charge wasn't something that he was completely willing to agree with.

Once she showed even the slightest bit of weakness, simply in the form of not pinning him to the ground any longer, he forced his hands onto her hips and started to thrust as much as he possibly could. Slamming in again and again as he matched the pace of her constant bouncing. He had his needs, and she had hers. And one way or another, both of them were going to end up satisfied..!

The tiger siblings kept on moaning and letting their moans echo out around them. Tai thrusting as wildly as he possibly could, while Gaoko met his thrusts with her bouncing body. They were locked in one of the most passionate bouts that two mates could take part in. Truly a test of their relationship. Not just as siblings, but as lovers. It was a relationship that would be considered taboo in every sense of the word, but they did not care.

They loved one another. It was why they were able to stay sane despite their transformations. It was why Gaoko had gone through all the trouble of making herself stronger for his sake. And though it was why he had started to transform, it was also why they were able to go through all of this without any permanent damage to their personalities. This kind of breeding, fueled by their frenzied heat, was ultimately little more than an expression of their love for one another.

"TAAAAAAI!" Gaoko cried out as she tried to force her dominance over the situation by slamming harder and harder. She wanted to cum, she wanted him to fill her, she wanted so much and he would give her everything that she wanted. That was what the heat inside her told her, and she wasn't about to think that it was giving her the wrong signals!

"GAOKO-NEE!" And he wanted all of that just as much. No matter how hard she bounced, no matter how fast, he used as much of his power as he had available to keep her at his pace. While at the same time thrusting as fast as he possibly could, matching her as much as one could expect a boy like him to. It was a dance of pure passion, one formed through nothing but bounces and thrusts. Truly a show of the most potent kind of love...

Their insistence on taking control eventually led to both of them crying out as loud as they possibly could, their pleasures mixing together as their climactic cries filled the air around them. And from there, nothing could stop them from letting everything pour out. Nothing would stop those two loving siblings from making a complete mess of each other.

For Tai, the cum just kept on pouring inward. So much of his sticky white gunk poured into his older sister's hole. Honestly, it was rather absurd to see him cum that much. But that was probably one of the benefits that he had gained from his transformation. The sheer amount of baby batter that he was able to put out. There was no chance that she wouldn't be knocked up... That is, if she hadn't been pregnant already. But that just meant that all of this seed that poured into her would guarantee a few siblings...

And Gaoko... Well, to say that her pussy ended up looking like a waterfall would be the understatement of the century. Her pussy just let loose as much of her sticky juices as it possibly could. Utterly drowning the cock that was stuck inside her, all thanks to how much it had pounded her. There's no way that she was going to be able to walk after this orgasm, at least for the next few hours. Not that she'd want to walk, especially after how much he had filled her in turn.

Little by little, the veil of their heat started to lift, and both were forced to confront what they had done. And naturally, a massive blush started to fill their cheeks. Not only had Gaoko gone mad with lust, but so had Tai. Both siblings had embraced everything that should've made Monsters a bad thing...

And yet here they were. Looking at one another. Looking at the shame that filled them... And laughing it off, because they were there for one another. It didn't matter that they went mad, because they were able to recover. All thanks to the love they had for one another.

"I love you, Gaoko-nee..." Tai muttered as he hugged her as tightly as he possibly could, snuggling into her strong yet soft body...

"I love you too, Tai." Gaoko muttered in turn, making sure to hug him close and let him get as comfortable as possible. So small and so adorable, just the way she liked him...

And while the two slowly started to drift off thanks to the exhaustion of their breeding being too much for the two of them, a friendly observer couldn't help but chuckle a little at the sight of their love leading them down this path.

"Guess they won't be needing me any longer." The merchant that helped them out in the past whispered to herself, as she got up and started the long trek to the next village that needed her wares.

A Gyoubu-Danuki like her wouldn't miss out on the chance to sell happiness to those that needed it...