Disclaimer: I do not own Fate/Stay Night, it is owned by Kinoko Nasu.

The Tohsaka Clan War

Prologue

Morning was warm and humid over the suburbs of Fuyuki City, the sound of cicadas steadily droning in the background, the day already building to the heat of the summer at noon. Amidst the suburbs, a large, western-style mansion stood in the middle of expansive grounds, great iron gates standing closed through the outer wall that surrounded the latter.

The placard to one side of the gate read 'Tohsaka'.

Not far from the gate, a young woman on a black motorbike with silver highlights slowed to a halt, and switching off her machine pulled off her helmet. Like the motorbike it was black, with twin silver wings painted on either side of the visor.

Running a hand through her hair, the young woman anchored her motorbike, and getting off hung her helmet on a handlebar. Unlocking and opening the seat compartment, a pair of small dolls that were mirror images of the young woman if dressed like maids floated out, and settled themselves on her shoulders.

"Well," the young woman said. "Here we are, Hourai and Shourai. Where it all began."

The young woman smiled and stared at the mansion visible over the wall.

"Crest?"

Master and apprentice stared at each other in their shared workshop, the former seated at her desk, and the latter standing beside her. The master was a bespectacled woman with long red hair tied back in a ponytail, dressed in a button-down blouse and light brown pants and matching shoes. Her blouse had long sleeves, but they were rolled up to her elbows.

In contrast, the apprentice was a girl of ten, with bob-cut, shoulder-length, dark-brown hair. Like her master she wore a white, button-down blouse, though hers had short sleeves and were trimmed in black. Her knee-length skirt was patterned like a checkerboard in black and white, and along with her black apron and shoes sharply contrasted with her blouse and white stockings.

"You want a crest?" the master asked.

The apprentice fidgeted. "Y-yes." She fumbled. "Though, I didn't mean…that is…I wasn't…asking to have yours, since I'm not blood-related and so I can't have it. And even if I could, it's not like it's too late for you to have kids…well that's…"

The master sighed as her apprentice trailed off. "Why do you even want a crest in the first place?" she asked.

"Why wouldn't I want one?" the apprentice asked. "A crest is useful, isn't it? It's the…crystallization, of a magus and their ancestors' magecraft, and makes it easier to cast their spells. Also, don't they stabilize unstable mysteries? And in case of critical injury, they can…"

"Yes, yes," the master said, waving a hand in the air. "I know what a crest is, conceptually-speaking. I also know what they can do, and how useful they are. But, for all that they're a massive pain in the ass."

"Huh?"

"What, did you think inheriting a crest is a simple matter?"

"Of course not," the apprentice said. "I know implantation is a painful process, and afterward you need to take special drugs to stabilize it, and even with that and bloodline affinity, there's still a chance of rejection and other complications."

"And at times even when inactive they act up." The master said with a nod. "I know. Back when I was a kid I heard my…predecessor, complain about his crest at times."

The apprentice blinked. "What about you, master?" she asked. "Doesn't your crest act up sometimes?"

"I don't have a crest." The master said with a touch of bitterness, and smiled slightly at the mixed expression of surprise and regret on her apprentice's face. "Don't worry, I'm not going to get angry for you bringing it up. I should have told you I guess, in hindsight, about my not having a crest, and why that's the case. Though, that's a story for another time…and it's…no, not really…old bile, that is…"

The master trailed off, muttering to herself, while her apprentice silently looked on and listened. After several moments the master turned back to her apprentice. "Another reason why crests are a massive pain in the neck is that inheritance of crests often cause…well, fights and arguments, inside families, over the inheritance." The master said. "It sounds so simple, but 'heir and a spare' is not nearly as simple as it sounds. I know that quite well, and so do you, don't you, my little runaway apprentice?"

The apprentice looked away with a slight blush, and the master smiled and shrugged. "Anyway," she said. "While I know crests are…more trouble than they worth, or at least they seem that way, I also know useful they can be. Gods know how much easier things would be for me if I had a crest, though if I did I probably wouldn't be here right now…"

The master trailed off, leaving her apprentice looking at her in curiosity. "A story for another day," the master said with a small laugh. "Well, if you want a crest, you can get one using either of two ways."

"Oh?"

"The first is you make your own." The master said. "That said, since you'll be starting from scratch it won't be as useful as an actual crest is, if at all, since you won't be so much as having one as you are building one.'

"Huh?" the apprentice said. "But I thought that all magi of a lineage add to a crest so how…?"

The master scratched her head. "How to say this in simple terms…" she muttered. "Exactly…that: they're just adding to a crest. You would be building one. Or rather you are preparing the core for them to add to, and for them to use…"

The master trailed off and scratched her head again. "Hmm…let's put this in a more…step by step manner…" she said. "Alright, when you make a crest, you first need to find the right spot in your body to implant it – the core of what would be your magic crest – in, and then you need to find something with sufficient…conceptual weight, and affinity to your magecraft, to serve as a core. With me so far?"

The apprentice nodded. "Usually," the master continued. "A core takes the form of a mystic code, part of or your actual magnum opus, or a preserved fragment of a Phantasmal Species with an affinity for your magecraft."

"…I…don't think I can start making one yet."

"No, I don't think so either." The master said with a smile. "You're still at least ten years away from beginning to work on your magnum opus, and a preserved fragment of a Phantasmal Species is…extremely rare and expensive to find much less obtain. Not to mention, considering the rarity of your Sorcery Trait, well, I think using your magnum opus or a part of it as the core of your prospective crest might be more in line than finding a Phantasmal Species attuned to you."

"Are you sure there won't be?"

"There might be." The master admitted. "But Phantasmal Species rarely appear on this side of the World these days, so much so that…"

"…it's on par with True Magic." The apprentice finished with a sigh. "I know. Even if there are Phantasmal Species with an affinity for my magecraft, the chances of them appearing much less there would be existing samples of them I could use…"

The apprentice trailed off with a sigh, and nodded at her master. "I get your point." She said. "I think I also get why even if I start making a crest, I won't really be able to use it."

"Oh?"

"It's basically just raw material. Kind of like ore, isn't it?" the apprentice asked. "And by implanting it in me and…attuning it to my concepts, it's like refining the ore into something useful. But I can't really use it. And it's more dangerous than actually inheriting a crest, as there's a bigger chance of failure and rejection."

"Pretty much," the master said with a shrug. "And of course, it doesn't have magic circuits like an actual crest would have, so there's nothing to use. It's your heir and successor who'd first to truly be able to use it, as he'll inherit the attuned crest and the magic circuits that come with it. You understand how, don't you?"

"Yes." The apprentice said with a nod. "When I pass it on, I remove the magic circuits into which the core was implanted, and then…re-forge them, into a more stable form. My successor inherits them…"

"…and he uses them and continues to attune them to your lineage's concepts," the master continued with a nod. "And when it's his turn to pass them on he removes the crest along with the circuits into which it was implanted, re-forges them again, and then implants it into the successor…and it goes on and on…"

"…passed on from one generation to another," the apprentice said with a nod. "Each generation further…deepening, the concepts imprinted on the crest, and adding more magical potential and refining it as it goes."

The apprentice sighed. "Sorry kid," her master told her. "That's just how it goes. When you make a crest, it's not for your own sake, it's for those who'll follow in your footsteps."

"What about you, master?" the apprentice asked. "Are you planning on making your own crest eventually?"

"Maybe…" the master said after a moment's thought. "I haven't planned on it, but I might, or I might not."

The master paused, and with a smile ruffled her apprentice's hair. "Well," she said. "If you want to make your crest, you'll have to wait a few more years at least before you can start making one. And you'll need the detailed procedures for it, which I don't have right now, though I can get them if you or I ever decide to go down that path."

The apprentice nodded but was silent in thought for several moments. The master looked on in silence, and then the apprentice spoke up.

"You said there were two ways for me to get a crest." She said. "What's the second?"

The master smiled. "Go steal your family's crest." She said.

"Huh?"

"Surprised?"

"But I can't do that!" the apprentice protested. "I'm not a thief!"

"But you're a magus." The master said coldly. "And when it comes to advancing their magecraft, magi should not hesitate to do what needs to be done to advance their path to the Root. Not even to spy on and steal from other magi if their secrets and mysteries and artifacts are of use to you…even if they are family…"

The master paused, and laughed with a bitter note of irony. "I guess that makes me a hypocrite," she said mockingly. "Then again, it's not like Humans were born not to be hypocrites, much less magi…"

Closing her eyes, the master took a deep breath before looking back at her apprentice. "Though," she said, and patting the girl on the head. "If you don't want to steal it, challenge the heir for it in battle. Then you can at least claim it on grounds of right of conquest."

The apprentice lowered her face, troubled and weighed down by thought. "Anyway," the master said, getting up from her chair and putting a hand on her apprentice's shoulder. "You're still years away from being able to challenge your sister, my little runaway."

The apprentice nodded, and then to her surprise found her master's fingers under her chin, gently but firmly pushing her face up to meet her master's eyes, the woman having crouched down to her level. "It's completely up to you, whether you want to challenge her or not," she said. "But right now, we have more important things to do, don't we?"

"Yes, master. Sorry for wasting time."

"No, it's fine." The master said, getting to her feet. "It's not like this was something you didn't need to know or be taught about…anyway, you have chores to do, right?"

The apprentice nodded, and the master nodded back. "Then get to it," she said with an encouraging pat on the girl's head, and getting to her feet. "Those limbs won't finish themselves on their own, you know."

"Yes, master."

"And this is where it will end…or will it?" Sakura Tohsaka muttered, and narrowed her eyes. "No…it's just the beginning of the end."

Closing her eyes, she sighed and leaned back against her motorbike. She'd spent the months since her sister had left the country with her apprentice and boyfriend for London and the Clock Tower, watching through the eyes of her familiars and gathering the routine of the only person left behind.

The same person that would allow Sakura to pass through the bounded fields without needing to bring them down, and set into motion her plan to supplant her sister as the inheritor of the Tohsaka Clan. Though, just in case that wouldn't work, her familiars had also gathered plenty of information on the structure, design, strengths and weaknesses of the bounded fields surrounding the Tohsaka property.

"Not bad dad, not bad at all…" Sakura thought as she thought of the bounded fields protecting the mansion before them. She ran through them in her head, along with her prepared plans and designs to bring them down just in case, silently busying herself for the next several minutes, until the sound of approaching footsteps drew her attention.

Turning her head, Sakura noted the approaching figure of her mother, Aoi Tohsaka. She was older now, with touches of grey to her hair, but she was still the same beautiful woman in Sakura's memories…

…and closing her eyes, Sakura crushed the desire to run to her, to introduce herself, to embrace her and be part of one big happy family again…

Sakura, you will be given to the Matou family, to become their heiress…after they take custody of you, you will not be part of this family anymore…I'm sorry…it's for the best…

"For the best, huh, dad?" Sakura thought to herself with a smile. "There are a lot of things I've done and regretted or think were stupid…but running away was not one of them. And I will be part of the family…even if I have to force the issue."

As Aoi Tohsaka passed by with her fresh groceries, the mental image of bright flame erupting in the darkness sent prana burning through Sakura's circuits. "Excuse me, mom." Sakura said. "But, I think you can help me with something, can't you?"

Aoi paused, and turned with a smile, her eyes wide and blank. "Of course my dear," she said happily, oblivious to the spell blanketing her mind. "Anything for you."

Sakura smiled, crushing the protests of her conscience with iron resolve. "Then shall we go in?" she asked. "I want to see the workshop and library, and other important things that I'll need."

"Yes, of course. Just follow me."

Let the games begin.

A/N

As Sakura said, let the games begin.

Not much to really say, though I wonder if anyone can correctly guess who Sakura's master was. It's not really that difficult, to be honest, there aren't that many redheaded magi of note in the Nasuverse. I'll give you two guesses but you're only going to need one.