[Semi-Twinning, Corruption]

One of the worst things that could possibly happen within Chaldea had suddenly occurred. A Beast had awoken, one of the Servants that had the potential to become one had embraced her nature and evolved to the form of one of Humanity's natural enemies.

Koyanskaya of the Dark. A vile fox that had managed to turn into a proper Beast, creating a space within the facility to ensure that she could keep gaining power, all by devouring the Servants and making them part of her existence. She had already managed to consume quite a few of the lesser Servants, which was how she had attained this form in the first place...

"You won't get away with this, Koyanskaya!" The Last Master of Chaldea, Gudako, cried out as the three Servants she had at her disposal quickly armed themselves. Three women that had taken such good care of her ever since she managed to summon them. Even though each of them looked at her with initial confusion when they had heeded her call, they were now so close that they were practically inseparable...

Minamoto no Raikou. Kiara Sesshoin. And Ibuki Douji. An Oni Slayer, a Nascent Beast, and the Daughter of Yamata no Orochi. Three powerful existences faced down the beast with all of their might, with their squishy and weak Master hiding behind them...

All while the Beast laughed in response to the opposition in front of her. "Oh, I'll get away with this alright. You know that you want to be mine, Master." Koyanskaya said, licking her soft lips as she peeked past the hair that hid away her eyes. Ever since she had evolved to the point where she could use her Beast powers, she had taken on such a drastically different aesthetic. Elegantly hiding her beauty while her lower half had become a mess of fur and different beastly body parts. She was like a beastly taur, and she was excessively brazen. Showing off her furred breasts, which were already distracting her Master in the process. "I'll take care of you. Of all humans. You'll be like the animals you've hunted down, but this time there'll be no hunter to put an end to you. Just eternal relief in servitude..."

Gudako trembled as she listened to those sweet and succulent words. She almost wanted to give in. Almost. But both Raikou and Ibuki got in front of her, to shield her from the wicked Beast's influence. All while Kiara giggled and wrapped her arms right around her lovely Master, to make sure that she wasn't being seduced by somebody other than her.

"You will not succeed, Beast!" Raikou cried out, brandishing her blade as electricity started to cover it. "I will slay you, just like the Oni that stood against Humanity in the past. Mommy won't let her Master down!" Even when she was determined to protect somebody that she held dear, her Berserker attitude still shone forth.

Ibuki grinned. When she had first been summoned, she wouldn't dream of fighting alongside a slayer of her own kind. But that didn't matter. That was the past. She was a relic from that time as well. Besides, as long as she kept up the good work, she'd get to party. And that was all she needed to work hard. "You heard the Mommy, fox! You're going down!" She laughed, all while brandishing her own blade. Oh, she was ready to break a fox in half right about now.

Gudako trembled and panted as her cheeks flushed bright red. She could feel what the Beast had tried to do to her. She could feel her heart pounding against her chest. She wanted it to stop. It was far, far too much. And yet she just couldn't stop the sensation from spreading. All while Kiara continued to slowly caress her head, giggling all the while.

Neither of her allies were aware of what she had done. But it was okay. She didn't expect them to understand. They always tried to shoot down all the wonderful ideas for nirvana that came to mind. All the ways that she could make her Master well and truly happy. But thanks to a little nudge, things would soon come to fruition...

Koyanskaya watched as both of those powerful ladies dashed towards her, their weapons primed and ready to carve her to bits. But by going on the offensive, they left themselves awfully open. Especially as Kiara let go of their Master, giving her exactly the opportunity that she needed...

The process of charming her Master was simple. She just put her hand up to her lips and blew a single kiss. A kiss that was consumed by the flames of her power as it flew faster and faster, until it made contact with the Master's chest. Sinking in and making her moan more and more as her eyes started to take on the same hue as the flaming tails that were sticking out of the back of her lower body...

"Master!" Ibuki and Raikou both cried out in shock as they were caught off guard. Not just by the fact that they weren't prepared for something like that, but because Kiara had very clearly pulled a fast one on them. If she hadn't been holding their Master, she might've been able to dodge it. What was her end goal..?

Gudako panted and gasped and trembled more and more as her eyes rolled around in her head. The power of the Beast's charm was far beyond what she could handle. Causing her to very quickly cum and collapse, resting on her knees as a pool started to grow on the ground below. A pool that seemed a little whiter and stickier than the kind of pools of pussy juice that normal girls would make.

"Stand, Master. And tell me your heart's deepest desires." Koyanskaya said, as each of her tails started to grow, slowly approaching the shocked combatants as she kept a close eye on her Master. Knowing what she'd say. Knowing exactly what she'd do...

The ginger-haired girl slowly stood up as she listened to what the beautiful, wonderful, almost divine fox was telling her to do... And as her Command Seals started to shine, she gave a single, hopelessly obsessed command. "I command you three to stand still and let Koyanskaya make you part of herrRRRRR!" And in the process of giving her command, her eyes rolled into the back of her head once more, the sheer delight of giving her Servants such a devious command being all that she needed to cum straight onto the floor below using her brand new cock. That throbbing mess that had grown in a matter of moments.

Just like that, each of the three Servants felt like they froze. All while Koyanskaya's tails crept closer and closer to their bodies. They weren't allowed to move. Just stand there and wait for them to become nourishment for the Beast. Something that felt like betrayal to the two women that had tried to protect their Master.

Both Raikou and Ibuki didn't get much of a chance to properly dwell on what their Master was feeling, before they were turned into little more than Mana to properly feed the Beast. Dissolving into light as they became sustenance, while another tail slowly crept towards Kiara.

Unlike the two that had felt betrayed, Kiara trembled in delight and gasped a little as it came closer. "You really went right for it, Koyanskaya... I hope you're happy with what I showed you." She giggled, licking her lips as she anticipated her own end. An end that she had orchestrated. Because she would never willingly give herself away otherwise.

Koyanskaya chuckled a little. "Oh yes. Learning about Master's weaknesses, learning about how she's always wanted to see her Servants be turned into nothing more than food for something greater... She's quite the degenerate. But that's why she's been such a perfect fit for the both of us, no?" The Beast laughed, not giving Kiara any chance to answer before she let her tail turn her into mana as well, trembling a little as that influx of energy started to fill her...

Gudako trembled as she heard that. She knew about her interests? O-Of course she did, she was so magnificent that there's no way that she wouldn't. B-But did that mean... T-That this was all for her? She would go through all this trouble to satisfy her, even if it seemed like she had betrayed her? A-Ahhhh!

The ginger-haired Master cried out as she was driven to a climax as she tried to process what she had just heard. All while she remained on her knees, panting and gasping as her mind raced. It felt so good to see her Servants disappear, it felt so unfathomably good...!

"Master! Master, please! You can still stop this..!"

Gudako's eyes widened as she looked towards the Beast, who was giggling as her lower section started to stretch and writhe. She didn't really care about the fact that those silly girls had managed to survive being absorbed. But if they were going to try and be encouraging, then...

Koyanskaya reached down and parted the rows of tits, as three bulges quickly started to grow from in between them. Three large bulges that grew and grew as the fur slowly moved away, revealing the erotic form of the three Servants that had been absorbed. With a few key differences as they managed to emerge from the Beast's fur.

Every single one of them were significantly bustier. To the point where their bosoms were weighing them down and threatening to make them fall right out of their furry prison. That, and the fact that they were completely naked. They were being displayed like a bunch of trophies, even though they were still living, breathing, and able to put up some sort of fight. Not much of one since their arms were still partly submerged and not properly materialized, but they could shake around and struggle. Much like Raikou had, as she called out to Gudako just moments prior.

"You're full of holes, fox!" Ibuki grinned, though she was blushing just like the Mommy that had kept her company. "And you, Kiara! What was that all about, what's the big deal with helping out this fox?!" She didn't forget who had wronged her, however, and turned her anger on the nun...

Kiara laughed in response, only to tremble and moan as well. It felt so good to be part of another. Well, she preferred if she was more figuratively part of Koyanskaya, to the point where she'd love if her tails were currently thrusting into her various holes and filling her up, but this was good enough. "This will allow us to reach Nirvana, my dear companions. Our Master wanted this for us, as well. She's the type of girl who wants to see everything crumble, because she has such a massive masochistic streak."

"You horny harlot!" Raikou shouted. If she had access to her arms, she would be choking Kiara out at this very moment. "Release us, Beast! You will not win, Master will come to her senses and allow us all to be free. You won't be able to win against us all once we have our bodies back under control!"

"Oho. You really think she'd do something like that? When she could help all three of you fall even further?" Koyanskaya said, all while snapping her fingers. Causing a draft to suddenly brush against all three of the Servants that were lined up underneath her, a draft that shouldn't happen. After all, they were stuck inside her. So how was that possible..?

Both Raikou and Ibuki stared straight ahead as they blushed and realized what had happened. Their lower bodies, mostly comprised of their asses and a little bit of their thighs, stuck out of thin air and surrounded the ginger-haired Master. Practically surrounding her with their most precious areas, as if they were begging her to stick it in and breed them...

Well, it wasn't as if Kiara was begging her to stick it in. No, she was actively encouraging it. "Come on, Master. You know you want to. Just stick it in. You won't hurt us. It'll feel so good. It'll be the perfect way to treat us. As objects for you to use and abuse. Nothing but holes..."

Gudako trembled as she listened. She really did want to. But the tiniest bit of her heart was refusing to go along with it. Even if this was something that the wonderful Koyanskaya had done to appease her. "I-I..."

"Don't forget." Koyanskaya giggled as she slowly blew another kiss towards her Master. "If you stick it in, they'll become part of me. In every single way. My spawn. My daughters. My loving minions. Beasts in every sense, though still subservient to me. All you have to do is stick it in." That giggling erupted into proper laughter. Because she knew that she wouldn't be able to resist the allure of ruining everything she had worked for.

Indeed, the sound of Koyanskaya's voice was all that she needed. But having everything laid out in this way, with the gravity of her actions dwelling on her mind... She...

Raikou's eyes suddenly rolled into the back of her head as she felt a cock slam straight into her pussy. Oh god, it felt intense. It was thick, it was fast, and it was slamming so hard into her that it felt like something was going to break at any moment. And the worst part of it was how she just wanted it to keep going. She wanted it to last forever. She wasn't that kind of woman to indulge like this, but..!

It felt so fantastic. It felt like her mind was shattering the more she felt the cock slamming into her. More and more of her Saint Graph was cracking. If this kept up, then she wouldn't be able to stay the same. But it was okay. At least, that's what the quiet voice inside her mind was telling her. It was okay to give into the pleasure. It was okay to lose herself and become another Beast.

Raikou let out a deep and intense cry as fur slowly started to creep up her body. Fur that made her sprout the exact same kind of breasts that had grown from the lower part of Koyanskaya's body. Fur that made her look almost like the wicked fox that had absorbed part of her...

Until her hair grew and ended up covering her face just as Koyanskaya's hair did. Complete with a set of horns poking out from the sides of her head, letting her look just as erotically elegant as the Beast she had sprouted from. Just in time for her to feel the cum sputtering around inside her.

Ibuki had been watching all of this happen to Raikou. And she had to admit, it did look like it was a bit too much for somebody like her to handle. But she was an Oni. She could handle a cock. Besides, she had slept around with Kintoki during those nice parties. It wasn't like she was going to have a problem with a co-

Her eyes spun around inside her head as she let out a howling scream of pleasure, the fur immediately creeping up her body as she was corrupted at a much brisker pace. She could feel the Beast's essence rushing inside her, but it didn't matter now. It just felt good to be fucked. She wanted it more and more. So, so much more..!

Ibuki's hair quickly covered her eyes as her horns grew ever longer, making her look just as beastly as Koyanskaya. Complete with that hefty set of tits that grew beneath her main set. That alluring set of mammaries that would make anybody feel the need to pin her down and breed her...

And finally, there was Kiara. Kiara didn't even bother resisting as Gudako shoved her cock into her hole. She could feel the fur creeping along her instantly, causing her to gasp and moan that much more. Even the growth of her breasts was enough to make her cum and squeeze down on that shaft. It always felt so wonderful to just indulge like this. Even if this would mark the end of her life as a helpful Servant... Ah well, servitude and eventual nirvana was worth it...

"You really were a useful asset, Kiara." Koyanskaya grinned as she watched Kiara's transformation very quickly finish without much fanfare. That horny nun had been the crux of all of this. If she hadn't told her about her Master's fetishes, she would've had to wait much longer before she could put her plan into action. "Maybe it's not so bad to rely on another Beast, if they're all this horny."

"As for you two..." The wicked fox grinned as she looked down at the converted Raikou and Ibuki. Both drooling and gasping as they were still not used to their beastly forms. "A mighty Oni Slayer, and the Daughter of that detestable snake. And yet you both crumbled thanks to a human's cock. You really are embarrassing!" She laughed, with neither of them able to react with much more than a few cries of delight.

Gudako gasped and panted as the wicked Fox made those wonderful pussies disappear, causing the Master to fall onto her rear as her cock still craved so much more. She wanted more. She wanted so much more..!

But it was okay. She just had to look up, and she had a veritable smorgasboard of tits to fuck. The three converted Beasts were now hovering over her, their rows upon rows of tits were right there, begging to be used. And behind them was the Beast that had absorbed them, giggling as she watched the Master quickly get right back to fucking away at those Servants she had helped corrupt...

All while three seals slowly appeared on the side of Koyanskaya's tit, her Master's authority absorbed through fucking those pseudo-beasts…