So, hot on the heels of Hadrian Kotomine comes another Fate/Stay Night crossover. This was actually a fusion of two ideas. I really, REALLY wanted to do a Harry/Medea story (and if Thunder Dragon is reading this, yes, I have long ago read the Shirou/Medea story Path of the King, and it's in my favourites, and it is a mild inspiration for the story), and I had recently posted a challenge called 'Harry Tohsaka'. So, I thought, why not combine both? Harry is 20, admittedly, albeit through timey-wimey parallel world shenanigans, despite being Rin's twin (still makes Medea a cougar, though).

Also, this story actually feels like it has a lot more potential than Hadrian Kotomine (which will still be published eventually: there's already six completed chapters). Having started watching the Unlimited Blade Works TV series (at long last), I actually like how much more character development it gave Rin, compared to the original Fate/Stay Night anime. She was pretty unlikeable in the original anime, whereas she starts off much more likeable in Unlimited Blade Works. The UBW version of Rin is certainly one of the few tsundere characters I actually like. Mela Lee's improved performance also helps. Anyway, I thought she'd make an interesting foil to Harry. She's a wannabe cold-hearted Magus, and he's a jaded, but still altruistic hero, something that'd also make him an interesting contrast to Shirou, Archer, and Arturia.

Anyway, the prologue begins at the beginning of Unlimited Blade Works (albeit with elements from the Fate and Heaven's Feel storylines being brought in). But the chapters after it will focus on Harry adjusting to a new life in the Nasuverse, and Rin (and Sakura) adjusting to having a brother come up out of nowhere, as well as how Harry gains Medea as a Servant.

Oh, and finally, before I go, there is an EXCELLENT Abridged Series version of Fate/Stay Night: Unlimited Blade Works by BlazingAzureCrow. If you want to hear Archer being called 'Actually Satan' by Rin, Shirou have an obsession with saving pipes, an even more murderous Archer, and what is probably the most heartwarming version of Arturia's summoning (and no, I am not making this up), watch it.

SEPARATED AT BIRTH

PROLOGUE:

AN ARCHER'S CONFUSION

The Throne of Heroes. An abstract location located apart from known reality. Some thought of it as Valhalla. Others thought of it as something more abstract than a mere afterlife, like a noosphere, brought about by the collective consciousness of life in their need for heroes. Magi have spent centuries debating the true nature of the Throne, but the one thing that could not be disputed was the fact that it existed. The proof occurred every six decades in the Japanese city of Fuyuki, even if that was only known to the secretive Magi.

It held all manner of Heroic Spirits, even those that didn't seem that heroic. After all, one person's hero could be another's villain. And it even included rather unconventional beings to be called 'heroes'. Namely, the Counter-Guardians.

These were entities who had made deals with either the consciousness of Earth, Gaia, or the collective will of humanity, Alaya. Their mission was to stamp out any threats to the safety of the world, no matter what the cost. Many of them were damned souls tricked into Mephistophelean pacts.

One such Counter-Guardian was the entity known as EMIYA. While made of at least two souls with that damned name, the one we are looking at is the man once known as Shirou Emiya. A boy infected by the ideals his adoptive father once possessed, but had discarded to pursue the life of an assassin. That infection proved malignant, having taken root in rich soil, twisting and warping an already distorted, self-sacrificing personality.

He made a career out of being a hero…until circumstances forced him to make a deal with Alaya. It would have been better to make a deal with the Devil. At least the Devil was actually sadistic. But Alaya was utterly impersonal and indifferent to the suffering it caused Shirou. All it wanted was an attack hound it could point at people to kill, and those people would die. This was what his father did in life. So in a perverse manner, Shirou was continuing the family business in what passed for an afterlife.

But he had a potential opportunity to deal with this situation. EMIYA knew that he would be summoned to at least one iteration of the Fifth Holy Grail War, as the Archer Servant of his former friend Rin Tohsaka. If he could, he would take the opportunity to kill his past self before he could make the contract with Alaya. With luck, the time paradox that resulted would erase EMIYA from existence. If not…well, at least he tried.

Suddenly, he felt the pull, and smiled sardonically. He could hear her words as she chanted. "For the origin, silver and steel. For the cornerstone, gem and the Archduke of Contracts. For the ancestor, my great master Schweinorg. The alighted wind becomes a wall. Close the gates in the four directions. From the crown, come forth. Trace the three-forked road leading to the kingdom. Fill, fill, fill, fill, fill. Repeat fivefold, and when each is filled, destroy it."

Well, here goes nothing, EMIYA thought. No, Archer. He needed to think of himself as Archer. Emiya was the boy he wanted to destroy, the thoughtless boy who condemned himself to eternal suffering because of his damned ideals. Ideals he had drowned in, and become a monster.

Then, the pull intensified, and the climactic chant began. He felt himself falling through time and relative dimensions in space, while he heard her voice speak…

"Heed my words. My will creates your body, and your sword creates my destiny. If you heed the Grail's call, and obey my will and reason, then answer my summoning! I hereby swear that I shall be all the good in the world, that I shall defeat all evil in the world! Seventh Heaven clad, and the great words of power, come forth from the circle of bindings, Guardian of the Scales!"

Everything dissolved into a flare of actinic light…

…And then, he was in freefall. There was something rather Pythonesque, he reflected, in what was about to happen. While he wanted to wreck people's shit in the Grail War, he didn't want to wreck Rin's house.

He didn't scream…though he was tempted to whoop and holler. Instead, he thought, Trace On. His Servant body could withstand the impact, true, but it didn't hurt to be careful when one was falling at terminal velocity. Reinforcement was just an insurance policy more than anything. He looked down, and noticed Tohsaka Manor coming up to meet him like a cream pie to the face in some slapstick routine. Yep, Alaya, along with just about every other fucker with a sliver of omnipotence and a bad sense of humour, had it out for him.

And then, with a great crash, he smashed through the roof of Tohsaka Manor, landing on his face. It didn't really hurt…well, his dignity got a little bruised, but it had suffered worse injuries than that. He'd live…well, at least until the time had come to sodomise causality more than Gáe Bolg did. Speaking of which, he was looking forward to trolling Cú Chulainn this time around. That bastard was going to get it for shoving that damned penis spear into his chest.

He got to his feet, and arranged himself on a nearby lounge, making it seemed like he landed on it. Yes, just like that. Look just the right kind of badass.

Archer frowned when he heard footsteps coming up the stairs. This wouldn't be that problematic: he was expecting Rin to make an appearance. But his sharp ears picked up at least one other set of footsteps. And he was certain Rin was living alone at this juncture.

The door burst open, and Rin rushed in. Ah, seeing her was so nostalgic. The dark hair done up in twin pigtails, the aqua eyes…that ridiculously short skirt she wore when not at school…

But she was accompanied by someone else. Not Shirou, and not anyone he was familiar with from that life. In fact, he wasn't sure who the hell this was at all.

For one thing, he wasn't Japanese. He was European, with dark, messy hair, emerald eyes peering out from behind glasses. A lightning bolt-shaped scar zigzagged from beneath his fringe. He appeared to be a few years Rin's senior, maybe in his early twenties even.

And yet, despite the lack of oriental features, there was something about the young man's appearance that seemed very much like Rin's. The shape of the face, the intensity of the expression…and there was the way he kept close to Rin. Not a boyfriend…but a sibling? But Rin didn't have any siblings, barring Sakura, and she had been adopted out to the Matou family.

Then, the next surprise of the evening came. The young man spoke in English, rather than Japanese. "Is this really a Servant?"

"Of course he is. He must be," Rin declared. She then frowned. "But is he a Saber?"

No luck there, Archer thought. He gave them a wink and a cocky smirk.

"We told you about the clocks, remember?" the young man groaned, palming his face. "But no, once you get it into your head…I thought Hermione was stubborn at times. Have you been taking notes from her?"

"Oh, be quiet for a moment!" Rin snapped. Taking some deep, calming breaths, Rin seemed to resolve herself to make the best of a bad lot. "You there! What class of Servant are you meant to be?"

Archer scoffed. Never change, Rin, he thought with a nostalgic pang in his chest. Out loud, he said, "And what kind of question is that? We've only just met. What an unusual little Master I've been summoned by. Then again, maybe I'm the one who got the short end of the stick."

"Oh great, you summoned the Troll class of Servant," the young man said with a flat look. "Call Zelretch, he's probably missing one of his apprentices."

Archer actually had to stop himself from chuckling. That was pretty funny. Rin, meanwhile, asked, "Are you my Servant? And nobody else's? I'm making sure we understand one another off the bat."

"Sure. But where is the evidence that you are my Master?"

Rin showed off her Command Seals. "Right here. That should be all you need to know."

Archer was about to retort, trolling Rin, before he heard a familiar, and unwelcome, voice intrude. "Actually, aside from your Command Seals, I can tell that there is a mana flow between you two." A hooded, robed shape materialised next to the young man. A very familiar robed shape. "Your Servant is merely being insolent in the name of what he believes is humour. I don't know whether to applaud or rebuke him," purred the sultry voice of a too-familiar witch.

"Caster, poke not the Tsundere Missile, for it may go off in our faces," the young man sighed quietly.

Oh shit, oh shit, OH FUCK, what is SHE doing here?! Archer yelled within the confines of his skull. He fought to keep as much surprise as possible off his face, only allowing the bare minimum to show. The sort of surprise at having another Servant present. "And what is another Servant doing here?" he asked, trying to keep as calm as he could. With mixed success. He wasn't actually scared of this witch, he could deal with her easily enough if he wanted to, but her being here presented a variable he hadn't accounted for, more so than this young man being here. He hadn't been in this time for five minutes, and already he was lost.

Was Rin under that witch's control? Was this young man controlling her through Caster?

"She's my brother's Servant. Well, she is now," Rin said. "Caster was summoned by another Magus, but they had…a falling out. Not that I'm happy allowing a stray in the house after betraying her Master, but..."

"You weren't complaining when I gave you pointers on working on that Mystic Code for that Dead Apostle with the appalling sense of humour," Caster remarked. "Or enhanced those faded Bounded Fields around your home. And I'm still formulating that ritual for those vile things in your sister."

The young man sighed. "Caster, Sis, play nice." He looked over at Archer, his emerald eyes meeting Archer's silver ones. Archer was struck by how much those emerald-coloured eyes reminded him of Saber's, of Arturia Pendragon, the young woman known to history as King Arthur. The love he had lost. Not quite the look of a king, but certainly the look of a seasoned warrior, and too young too. "My twin sister and I have an alliance, at least until the final stage of the Grail War."

"Your twin sister? You don't look that much alike. You look Caucasian, and she looks Japanese. Not to mention she looks younger than you," Archer said.

"It's a very long story involving a kidnapping and a blood adoption in another world," the young man said. "Time flows between different universes are weird. I'm twenty, Rin's seventeen. All of which meant that she got the Magic Crest. I don't mind."

"Because you've got that stupid magic from that other world," Rin retorted. "That is so unfair."

"Should I get some popcorn?" Caster asked. "I get a craving for some while watching you two bicker. I wish we had that back in my time. You argue like an old married couple, only with the additional frisson of incest involved. Though given the blood adoption procedure, you're technically half-siblings now…"

"Caster. TMI," the young man said.

Archer looked askance at Rin. "And you trust your brother to fight alongside you, even though he is also an enemy Master?"

"He even signed a geas contract to that effect," Rin declared. "We both did. Until our Servants are the last ones standing, we cannot attack one another. We modified it so that we are in a coma for a month and we forfeit our privileges as Masters rather than losing our magic or our lives, but still…"

Archer wondered whether that was prudent or stupid. Still, two Masters and two Servants working together were better than one, though he had to wonder how trustworthy Caster was, given his prior experience.

The witch in question strutted over, and examined him critically, her eyes glinting out from beneath her hood. "Hmm…well, at least you're not my first husband. Alliance or not, I would have ended your existence forthwith if you were. You don't look like anyone I know either. Since there are only three classes left to draw, you're either a Saber, an Assassin, or an Archer. So, please answer Rin's question. Which class are you?"

"If you must know, I am an Archer. Though I have some tricks up my sleeve."

"I'm sure you do. I'd be interested to see them," Caster said with a smile.

Archer looked at the three of them. If it had only been Rin, he might have engaged in some ribbing, push her buttons and stoke her temper, make her remember how inexperienced she truly was. However, he didn't know how Caster or her Master would react, at least if he pushed her too far. With a weary sigh, he stood up. "Well, it seems like I am stuck with you, my Master. However, keep in mind that I will take the lead when it comes to tactics. Try not to get yourself killed."

"We watch each other's backs," the young man said. "Besides, magical tournament with possibly lethal consequences? Yeah, I've been there before. Not this Holy Grail War BS where we battle to the death for an overrated cup. But I've been there before. And in war."

He meant it. There was no lie in the boy's sardonic admission. Archer found himself feeling a little sorry. Another person who saw hell too young. "Incidentally, I'm curious. We Servants must conceal our name to conceal our weaknesses, but Masters are another matter. What's your name?"

"Harry. I thought my last name was Potter, but it was really Tohsaka. As I said, and hard thought it is to believe, I'm Rin's brother…"

PROLOGUE ANNOTATIONS:

So, there you have it. Harry's the brother of Rin Tohsaka, believe it or not, and he's the Master of Medea. Now, for the next few chapters, we'll have how Harry ended up at this point. In fairly abbreviated form, anyway.

No numbered annotations this time.