The Most Powerful Magus?

15 years old Okumura Rin grew up mostly alone because she got told that Yukio is training young to be a priest and the other guys got jobs to support the Monastery so she grew up mostly alone after school.

Life was go to school, do well, beat up her twin's bullies and maybe chuck them to a hospital or two, and dote on said twin while tending to his boo boos, and cuddle at night.

However one day at age 9, she met an old man with red eyes(she didn't know any better back then).

'Hey kiddo, you got talent.' he said. 'Wanna learn magic?'

Rin went sparkly eyed.

'Magic?! Like in anime like Sailor Moon and Magic Knight Rayearth?!' she squealed excitedly as the old man chuckled.

'Yup, but a bit different of course!' he said. 'I'll pick you up at a certain schedule, sooo keep it a secret OK?'

'OK~!' Rin chirped cheerfully.

Learning magic, was harder than she thought, but Rin in all her innocent mind persevered while learning combat skills too.

She was a natural talent enough to be known in the West as an 'insanely powerful genius' in Clock Tower. The number and quality of her circuits beyond compare. She was a fully-realized magus at age 15 and her family was none the wiser but as years went by, Yukio got 'manlier' since he no longer put up with being bullied and fought back for once.

She was a proud sister and glomped him.

But when she was 15, she had to move out after getting a job...so to keep her magecraft secret, move out she did but she was wondering...

'Hey dad, what jobs can middle schoolers usually get?' Rin asked her. 'I'm thinking of what to get but that depends on salary...'

'Rin, being a middle school graduate, the jobs are not glamorous but a job is still a job and money is still money.' said Fujimoto Shiro, the man she called father all her life with her twin. 'And you'll learn how to budget responsibly too.'

'Heee...'

At that point, her phone rang. 'S'cuse me...hello?' that, was English. 'Oh, its been a week since I finished those!' the priests and Yukio exchanged looks. Rin speaks an accented English like she lived in the west for years. 'Uh-huh...whoa...' her cheerful expression fell. '...hang on a mo', isn't that absolutely totally stupid of them?!' she cried shrilly, startling the dinner table. 'That's like, so dumb! Why'd they do it?!' she exclaimed incredulously. After a pause, she face-palmed. 'OOOOK? Everyone and their grandma's ancestor knows that'll NEVER happen in a million years and they still did it...' suddenly, she looked excited. '-oh, sure I'll take it! A job's a job and good timing too! Just send me a plane ticket!' she cried excitedly. 'Yup! Tell that old geezer I'm in! Yeah, yeah, See ya in London!'

'Er, Rin?' Shiro croaked out. 'Friends abroad?'

'Yup, they got me a job!' Rin said cheerfully. 'Goodness knows it'll pay more than here, I'm flying to London as soon as my ticket gets here!'

'So what's your job neesan?' Yukio asked her, interested.

'Oh, I got hired as a stalker.' her family spit-sprayed.

'C-come again?' Yukio choked, glasses going askew. 'S-stalker?!' he gasped incredulously in a high-pitched voice.

'Well, its a blunt, crass word for 'Investigator' isn't it?' Rin huffed. 'They'll never suspect a cute teenager following and investigating right? They scored me a Journalist job so I'm a-ok but I'll be taught the ropes first.' she said. 'They can't send their usual guys and need someone anonymous.'

'Hey hey, isn't journalism risky?' said Naoya worriedly.

'I'll be fine! Look at these guns!' Rin cried, and like imitating a boy, flexed(nonexistent) muscles on her skinny arm.

'You don't got any!' her family yelled in exasperation.

xxx

'Sheesh, are you serious about flying to London neesan?' Yukio asked worriedly as his(still childish) sister was still a cuddlebug and its really dangerous as they're both in their mid-teens since she presses her-well-developed-body on his and he fears their fifteenth birthday with reason.

'Yup. Hey, when opportunity falls on your lap, you grab it, don't be dumb to let the wind blow it away right?' Rin beamed. 'You got a scholarship on that highway-robbery school so don't waste it too alright? Its a big card to Todai too. It'll be a rough three years I'm worried about you.' she said. 'Balance schoolwork and relaxing or you'll crash, OK?'

'I'll be fine.' Yukio snorted.

Then his sister frowned, looking at something.

He followed her eyes, and saw a Coal Tar floating around their room.

Fuck.

Its happening already.

Her powers, their monastery's darkest secret, is awakening.

'...you sure have dust bunnies.' she commented. 'Are you cleaning your room since you forbade me to on weekly cleaning day?'

'I am!' Yukio grumbled, grabbing a mosquito spray that actually contained holy water. 'Go to sleep sis, I'll go bug-busting.'

'Ugh, you had to do that now?!' Rin whined as she covered her face with the blanket, allowing Yukio opportunity to kill the Coal Tar.

He was glad she thinks its a dust bunny.

He then dealt with his cuddling sister who was way too clingy on him still.

She never mentally grew up, having retained a child-like personality with bouts of violence when it came to him. She's not like most teenagers who grew up noticing the difference between boys and girls. At least she's responsible in the house, her schoolwork(her grades are above average) and cooking. Her interests and mindset however...nevermind her body, she's a late-bloomer in both mind and heart.

He really worries about her future and how long can she stay innocent and smile.

Its weird that for one with a frightening parentage, she's sweet and innocent.

xxx

Next day, she got her plane ticket after preparing her things, and dressed in a green jacket, a tube top and a pair of jeans and sneakers. Her long wild hair in a half-ponytail. She packed up her suitcase of clothes, necessities and documents needed for travel. But she would be driven to the airport.

'...so she can see...huh?' Shiro frowned as at the gardens while Rin cooked, Yukio told him she could see a Coal Tar.

'...I really doubt her safety abroad.' Yukio deadpanned. 'One of us should go to London too.'

'I wish we could but we need another minder.' Shiro twitched. 'You got school and your job and I got my job too. We barely have time that we mostly left your sister alone all these years which is why she's so clingy. We were hardly there for her while protecting her from afar. I wonder what happens sometimes when she's alone in the house while I'm training you.'

'...'

'...don't you get the feeling that somehow, something big happened behind our backs?'

'...from last night's incident? Yeah.' Yukio frowned. 'Her English in school and English last night were both different. She was faking it in school since she's much, much more fluent like a native. And she knew foreign people she got connections we don't know about. That worries me.'

'Let's look into it.' Shiro muttered. 'I wonder who she's hanging out with, when we're not looking.'

xxx

London, hours later...

'Waaah...I hate jet lag...this freaking sucks.' Rin groaned as she got off the plane, feeling totally out of it.

She picked up her bag in the Luggage Area, and left the terminal to a cab lane and hailed a taxi that she controlled into dropping her off in Clock Tower.

Upon bypassing the security fields, she went inside...and went for an office after going up several flights of stairs.

She met up with her mentor.

Kischur Zelretch Schweinorg.

An over-900 years old Vampire, an Ancestor-Class Dead Apostle. One of Clock Tower's strongest magi, a Wizard Marshall and Magician.

'Shishou, I'm here.' she said as she sat down on the couch. 'Stupidity aside, any new developments?'

'Yeah. The Association sent fifty elite magi to take it back...only one survived to activate the Grail's Emergency Function and came back insane.' said Zelretch. 'Unlike a typical Grail War, its now a Grail War by two factions. Seven for us, seven for them, 28 people in total.'

'Its gonna be one-sided, knowing the association gramps.' said Rin. 'Lord Sophia-Ri's no slouch in scoring us powerful Servants and we got first-classes present...and they're a clan of a dying race to sum it up.'

'Yeah. But its entertaining to say the least, Darnic's arrogance.' Zelretch chuckled. 'Even he knows Yggdmillennia can never be a Clan Lord which is why he wants to secede his ragtag bunch of misfits and start their own association. If they ever succeed assuming they survive, they will not last long. Clock Tower has all magical resources and funding gathered here, and they don't got that much.'

'A fool's dream, basically.' Rin rolled her eyes. 'But 49 corpses meant that they got a Servant who mopped them up since they can't fight them all as Magi. They're too weak for that.'

'Indeed.' Zelretch took out a small box. 'Here is your catalyst. Only you are capable of comfortably supporting this fella. Other magi can't last as long. Even I can't. A battle is faster than me taking mana from many worlds to support upkeep. Bram indeed, is no Slouch. He acquired for us a Shard of the Round Table, Remnants of the Argo, a pair of Earrings belonging to your Servant himself, and our Berserker's Manacles. We are allied with the Church this time and they already got their own artifact for a Caster-class so we're all set.'

'I wonder about the situation Master.' Rin muttered with a frown. 'I've been in contact with Fiore Forvedge Yggdmillennia, my classmate in Fundamentals Class.' she said.

'Hooo?'

'Backing out is not an option. Even if she was Darnic's favorite, if she backed out, he wouldn't hesitate to cast her out with nothing. While they say Yggdmillennia seceded, in reality, its only Darnic who seceded, taking everyone with him because he said 'Yggdmillennia will secede'.'

'You put it that way eh?'

'Yeah. Fiore of all people has no such delusions of grandeur. Only fear. Her brother only has resignation since the spells appeared on him.' Rin commented. 'The other Masters however...are all for it, just as nuts.' she snorted. 'Fiore's the only one with actual brains, only in this for her own self-preservation and her brother who's just as unlucky in potential got dragged along. What do we do about that?'

'Well, that depends on their actions in this war.' said Zelretch. 'If we kill the others, the Forvedge will secede from the Yggdmillennia since she's its clan head. She surely will but Yggdmillenia's actions will damn her own clan. They'll have it rough and for history of magi in this place...it'll be a hard thing to forget.'

'Sou ne. Too bad for her she has morons for relatives. That's her misfortune.' Rin shook her head. 'In time, the Forvedge will disappear as well.' she took the earrings. 'Who are the other masters?'

'First-Class Lecturer Feend Vor Sembren. Rottweil Berzinsky, the Pentel brothers, Gene Rum...then there's you.' said Zelretch. 'Belfaban called in another guy. No thanks to that stunt we're in shortage of first-class Magi and you being hired is out of desperation. You just graduated Clock Tower a Brand, yet an unknown despite your immense powers. People wonder about your combat ability even though I vouched for you.'

'Aaand that's enough for me.' Rin grinned. 'Shishou knows full well how strong I am, let's just ignore the skeptics.' she said dismissively with a handwave before blinking. 'Oh yeah, one problem...' she piped up. 'If we succeed in defeating the Yggdmillennia and its still a Grail War...back to normal?'

'Indeed. You guys will fight and kill each other for the prize.' Zelretch grinned. 'That's what its about.'

'I knew it.' Rin chuckled. 'I don't even know what I'd want. Or if this dude will want something.' she said, looking at her earrings. 'Well, considering I told my family I got a journalist job thanks to some friends, I better not die. Heheh.'

'A journalist at fifteen?' Zelretch raised an eyebrow with a weird smile.

'In Japan, compulsory education is up to Middle School only, and after that you can get a job albeit a not-so-glamorous job. High School gets better jobs but my family's too poor to send both of us and to be a journalist in Japan, you gotta graduate college so I had to lie my way through. My brother got a scholarship with his grades so he can afford to go ahead but for how long he can hold onto it is the question.' Rin muttered. 'I'm taking an advanced downpayment shishou. In the event I die, erase my existence back home and put my remaining money in father's account so incase things go shirty, my brother will be OK. I'll be spending some of that in war after all.'

'Alright.' Zelretch took out a money envelope and gave it to her and she took it.

'Well, I'm off to call my guy shishou.' said Rin. 'Who's he by the way?' she asked, pointing at her earrings.

'From India, he is the Hero of Charity, Karna.'

'Ah, I'm off to India to call him out then. Gotta take what boon I can in return for another shitty jetlag. We're fighting idiots, but they probably got strong guys on their side, can't hurt to be too sure. Better sure than not.'

Zelretch snickered.

With that, Rin left for India after researching Karna in the library.

She had gone to his birthplace to summon him there, and used blood from a Slaughterhouse that she gathered to draw the summoning circle.

'Well, time to call my partner out.' she said as since she hasn't spent much mana during her trips, she's very full that she can give it her all in summoning her Servant.

Silver and Steel be the Essence.
Stone and the Archduke of Contracts be the Foundation.
Red, the color I pay tribute to.

The summoning circle started filling with mana and strong winds caused by the magic are starting to flow wildly.

A Wall to harbor the Raging Wind.
Let the Four Cardinal Gates be sealed
and tread the Three-Forked Road from the Crown
reaching unto the Kingdom.

Her command spells started glowing as the power of the Grail and her own power is starting to flow harder into the summoning. Slowly but surely, a pillar of light started forming from within the center, slowly filling the circle and spinning fiercely. The closer she came to end the ritual, the bigger and faster the spinning of magical energy...

I hereby propose!
Swear your Fealty to Me, and My Life shall be your sword.
If you abide the Grail's Summons and Follow the Laws, then Heed my Call.
I hereby swear that I shall be all the Good in the World.
That I shall destroy all the Evil in the World.
From the Seventh Heaven wielding the Three Words of Power,
Come forth from the Ring of Control, Guardian of the Scales!

A blinding flash of light, combined with strong winds made Rin wish she wore shades, had she known it'd be THIS flashy...

'...your summons has been answered.' Karna was too beautiful and ethereal in looks but clearly of hindu origins. Then again, he's half-god, of course no mere mortal could have looks like his. That would be an insult to this man! 'I am a Servant of Red, and my fate lies with the Association. My sword is your sword.'

Karna looked at his Master.

A young girl.

A powerful girl, if she could afford his upkeep. She didn't even look winded as Karna is fully-aware that while he is powerful, he is lethally-ruinous to maintain and yet this girl...what is she?

'Hello, Karna.' Rin greeted. 'I'm your Master, Rin. We're in for interesting times together.'