[Seductress TF, Corruption]

Defending human history from those that would seek to undo it is a hard task. Something that Chaldea, the last bastion of humanity, was very well aware of. It involved travelling through time and fighting against legendary and mythical figures for the chance to right what was made wrong, regardless of the consequences of their actions. The bonds that they had forged could be made undone just like the history that they had fixed, but the safety of those that came after was more important than the ones that came before.

There was just one other problem with defending the timeline. Not a moral one, but a logistical one rather. Namely… The mess that was made after the main Master of all the Servants that they employed finished his latest summoning session. The Saint Quartz, the catalysts that were used to bring the figures from the Throne to their side… They were very brittle. So every time he tossed them around in the room where the summoning took place, to cause that process to start, he spread a ton of fragments around to the detriment of anybody that was unfortunate enough to be saddled with cleaning duties for the day.

On this day, Mash Kyrielight, the Shielder Demi-Servant that had been by his side since the start of his journey, was stuck with this duty. And only now that she had the chance to get a proper look at the mess did she realize just how much he wasted them. There were slightly sharp pieces of quartz strewn across the floor, each of them waiting to be stepped on like loose pieces of lego. All of them constituting a hazard to the health of anybody foolish enough to step into this room… including herself and her Master.

“Senpai, you…” Mash muttered to herself as she shook her head slightly. The sight was terrible, but she had no room to complain. If not for his haphazard spending, they wouldn’t have all the allies that they did. So she had to grin and bear it for their sake, so she could bring it up to him next time they went to summon more Servants. Hopefully that would make him see reason…

Or he’d just ignore it and get really mad that he didn’t get the cute girls to appear again. As he always did. “Haaah… You exhaust me, Senpai…” The eggplant-haired girl muttered to herself as she reflected on his behavior. So callous, yet it was that disregard and open way of living that attracted her to him. She couldn’t help it, there was just a special kind of pull to him…

As the Shielder-class Demi-Servant continued sweeping the floor to try and gather all of the Quartz fragments into a single space, she didn’t notice how they were gradually being put back together. One fragment snapped together with another, then a pair, which then combined with three loose ones to form one complete Saint Quartz. A process that kept on repeating until there was a pile of proper Saint Quartz laying right there, ready to be used…

Unfortunately for dear Mash, as much as she no doubt wanted to go run off to her Senpai/Master and tell him about the load that he had left behind, she had neglected to take the shield out of the summoning system. And it was a sensitive device, taking any bumps as a sign that it was time to summon. Thus, as soon as she accidently pushed the tip of the broom into the pile, every single Saint Quartz dissolved into nothing as it was swallowed up by the room around her.

“W-Wait, I didn’t mean to summon! Who’s even going to be contracted, there’s no eligible Master in here!” The panic on the young girl’s face was easy to read, as the sweat ran down her brow. What was she going to do? She couldn’t just tell her Senpai that she had accidently used a good 30 or so of his precious rocks, he’d yell at her and get miserable if he didn’t see a cute girl… well, she was cute, so he’d probably just hug her and tell her it’s alright, but the terrible thought still lingered.

Her words were technically correct. There was no eligible Master in the room. But the summoning system was made with that in mind, something that she hadn’t been informed about. Whenever there wasn’t an appropriate Master to establish a contract with, the system picked the nearest possible vessel for a Servant to inhabit until that time could come. And that vessel… well, it just happened to be her.

Sparks started swirling around her, like they usually did whenever the two were summoning. During those moments, she held her shield aloft to gather the energy and make the Servant pop out there. Instead, they swirled around her at around waist level, making her sweat intensify in the process. What was going to happen, exactly..?

The sparking orbs that surounded her rapidly changed color from blue, to yellow, until they flashed every color of the rainbow to signify just how powerful the Servant that was about to be summoned was. Just her luck, it had to go from good, to bad, to terrific all at once. How could she even…

Before Mash’s thoughts reached a conclusion, the orbs gathered in her and caused her eyesight to black out immediately. She felt her consciousness slipping as she fell onto her back, collapsing in an instant. Her entire being fell quiet, and the light in her eyes faded… as the new soul slowly took root within her body. A process that required a ton of her body’s energy, otherwise it would just fizzle out without a result…

While the Shielder’s mind had shut down, her body started to change. Rather drastically so. Instead of the armored dress that she normally wore, that utterly plain thing was replaced with something much more fitting for her new host. A dress. But not just any dress, a dress that managed to expose as much skin while still looking dignified and regal.

Thighs left open thanks to a single strip of cloth that descended between her legs, obscuring just enough of her crotch to tease the onlooker. A diamond cut out on her stomach, exposing her navel and emphasizing a certain amount of fertility in the process. A top that just barely kept her breasts held up no matter how heavy they were, so that they always showed a degree of heft. As if they were full of something nutritious, something that only a true suitor might have a taste of…

Once the dress had replaced her garishly armored dress, her boots and her gloves needed to go just the same. The gentle creamy white that had started coloring her dress moved down her legs and across her arms until they reached the tips of both limbs, wrapping upward until it seemed like bandages had been applied to the limbs… Only for the color to solidify. Gloves that were made of delicate silk manifested through the color on her arms, and a set of stocking-connected heels clung snugly to her legs. She was stunning in every sense of the word now…

But those changes only concerned what she wore, not how she looked as a whole. Her body, the thing that she coveted most of all, still needed to be pushed along the right track. Her curves were meager, yet not completely hopeless. If Mash was still conscious, she might’ve just felt a set of phantasmal hands grasping onto her hips and slowly tugging them outward, making the meat on both legs grow in turn. Little by little, inch by inch. Until she had a pair of killer hips that seemed appropriate for a seasoned mother, while accompanied by an equally destructive pair of thighs that could crush any man, no matter how strong they might be.

Her top needed just as much work, though her arms were already delicate enough that she didn’t need much more than for her skin to shine just a little. An oily, elegant shine coated the parts of her body that hadn’t been captured within her dress, all while the breasts that were hefting out from that cleavage-cutout slowly filled out. With every soft and subdued breath that left the unconscious girl’s body, her breasts grew another cup, until they reached an exaggerated and utterly in-escapable H cup. It was a miracle that her dress could even withstand this size, but that just emphasized how much the new Servant was a match for her body…

Finally, with her body having taken a proper turn, it was about time for her mind to experience the same. Not that her mind would be her own, since the new existence within her shell of a body needed to stretch its own influence. And what an influence it was, as images of men prostrating before her, women at her beck and call, and most importantly a knight and his holy sword-wielding king each at her side, both ensnared by her wicked words… All of it felt so right, yet the specks of the Demi-Servant’s consciousness couldn’t quite understand who had taken up a seat within her head. Just that all of it…

All of it felt right, as a sly and wicked smile fell upon the unconscious girl’s face…

---

It had been some hours since the accident happened, and the Master of Chaldea, Ritsuka Fujimaru, finally realized that his beloved Kouhai had disappeared. He was a bit busy with the male Servants, as he had tried to prove that he was manly in his own way. Something that was quite difficult since he was just human compared to their mythical figures, but they always encouraged him to try his best.

But once his muscles had been worn out, he realized that his link to the young girl had grown strained. So he did what any good Master would do, nay, any good Senpai would do upon finding out that his Kouhai was likely in danger. He ran as fast as he could to the last place where she showed any sign of life. Which just so happened to be the Summoning Room, the place he usually got the most angry…

“Please be safe, Mash. If you are, I promise I won’t get angry over cute girls ever again..!” Ritsuka silently prayed as he stormed into the room, clearing his throat in the process. “MASH! MAAAAASH!” He immediately yelled, hoping that he could find her and embrace her like he always did…

What he hadn’t anticipated, was the sight of his beloved Kouhai on the floor. Unscathed. So that was nice at least, she wasn’t hurt. But she did look a little different. Had she put on makeup? No, she didn’t know about that stuff. He was sure of it, the last time one of the other Servants tried to help her, she ended up with her face chalk white until he finally pointed out that she looked like a clown. She swore it off after that, especially since he liked her without it. So, if not makeup, then…

“Mmmmm…” A soft, seductive tone slowly left the girl’s lips as she sat up, her eyes opening to reveal that her tender irises had gotten rather sharp. She even licked her lips in a rather provocative manner as she looked straight ahead at her Master, a grin forming on her lips. “My my… Senpai, you’re a sight for sore eyes…” She mused, her voice sounding uncharacteristically mature…

The black-haired Master felt a shiver run down his spine as his Kouhai got up on her feet, letting him well-and-truly take in just how hot she had gotten. Where was the eggplant with a pair of thin legs and breasts that, while not impressive, were still pleasant in their own right? Who had taken her and replaced her with this titty monster that seemed to be awfully interested in him? “Mash? Is that-”

“Of course it’s me, Senpai…” Mash giggled a little as she came closer, only to pull the boy into her bosom and trap him against her body. Not even a second passed after that before her natural pheromones, a sweet scent of lavender designed to captivate anybody that might get too close. The same weapon that had entranced so many men, according to the Servant that now occupied her body…

Ritsuka was flabbergasted and honestly pretty unable to do anything. As soon as that fragrance hit his nostrils, his expression melted into pure bliss. “Masssshhh…” He muttered, a bit of needy drool running down his chin as he nuzzled into those massive melons…

“Exactly, Senpai. You know what you want, and I’ll be happy to give it to you…” She was just as pleased with him as he was with her, as her heart skipped a couple of beats and her cheeks flushed red. Even with this new presence inside her, the love she held for him was still alive and well.

But that didn’t stop that influence in her from wanting more. And with her Senpai, no, her Master under her control… She could spread her own control….

“Senpai… Would you mind if we have a few talks with your Servants?” She asked, and the boy shook his head to agree. “Wonderful… Oh, yes… Would you allow me your Command Spells, while we have those talks? Just to make sure they’re in capable hands…”

He didn’t even answer, as the engravings on his hand slowly transferred onto one of Mash’s. Leaving her with all the control that she might want. And with that much power in her capable, loving hands… She knew exactly what she had to do.

Pay her beloved Senpai back for everything he had done for her, by giving him a harem that wouldn’t be able to refuse him. Maybe even make those silly boys that loved those women watch, just to rub in who owned their lovers from this point onward. Maybe then they’d realize who had taken root inside the Demi-Servant, without having a chance to pull her out...

“Just sit tight, Senpai. I’ll give you everything you deserve…”