Author's Note: I came up with this idea while almost completely deprived of sleep. I'm not sure this excuses anything, but... well, it's the best I can do.
Mind of Aluminum
Rin's eyes were colder than the heart of a glacier.
"The course of action is clear." She said firmly. "Sakura Matou is too dangerous to live. She could be made a tool for Zouken at any moment, and when that happens, she will kill us both. There is no other option but to end her life. It's a mercy for her, and the only safe course for us." Her voice was cold, distant, dead; the tone of a judge pronouncing final, absolute sentence, no room for compromise or debate.
The young man she was speaking to nodded once, sharply. He understood the necessity of her words, and he could not help but agree. "Yeah… we have to." Judge and jury had spoken. All that remained now was to swing down the executioner's axe.
Rin winced. "On the other hand…" She said.
"… wait, what? 'On the other hand'? You were acting all serious about this, how is there another hand?" The young man said. The icy tension in the air deflated like a balloon. It even made a 'phweeeeeee' sound, if a slightly imaginary one.
"Well, I mean, it seems like a waste, doesn't it? She's a rather pleasant girl. Makes excellent soup, has very good hair, looks nice in a sweater. I mean, you shouldn't just kill a girl like that out of hand, she obviously has superb genes. Just look at that bone structure." Rin said, very carefully not looking directly at the man she spoke to. "Tall, but not too tall, y'know? Girls who are too tall just don't look quite right, but she's a very nice height."
"Um. Erm. Okay…" The man said, running a hand through his hair in mild confusion. "So… let's… not kill her?"
"Oh, what now?"
"Well, it's just that she does have those worms. Her mana is dangerously unstable and she has an ancient evil wizard able to control her mind at will. I really do not like the thought of having to fight off Zouken in the body of a teenage girl. He's creepy enough as-is, you know? Of course you know."
"… ooooooookaaaaaaaay…" The man said. "So we do kill her, that's fine."
Rin winced. "But she has such wonderful taste in shoes. And an excellent singing voice!"
"Okay! Then she lives!"
"But the worms. Evil, evil things, those worms. Nasty."
"… … … are you just doing whatever the opposite of what I suggest is?" The boy asked, eyes narrowing in suspicion.
"… Noooooo." Rin said, doing her very best to not look him in the eye.
"Oh, really. Okay… what is your opinion of kittens?"
Rin smiled. "Cute and fluffy, I love them."
"Love to hate them, I mean. Can't abide the hideous little bastards. Basically just lizards with fur." Rin said.
"… I was thinking we could have stir fry for dinner."
"Hate it." Rin said.
"Yesterday you said it was your favorite meal."
"Oh, right, I did. Well, um… yes, I guess that's true…"
"Then why did you just say you hated it?" The young man asked.
"Because… I thought you said… stir… lye?" Rin said. Or asked. It wasn't clear if this was supposed to be a statement or a question.
"You thought I was suggesting we eat poison for dinner."
"… yeeeeeeeeees." Rin said carefully.
"Oh, come on, just admit it! You totally just do the opposite of whatever I suggest! This is the worst partnership ever." The young man said.
Rin winced. "In my defense, Shinji, I've been doing it the whole war and you only noticed just now, so it clearly wasn't too bad."
One Week Earlier…
Shinji Matou and Rin Tohsaka locked eyes across the rooftop.
"So what do you think, Tohsaka?" Shinji asked, smirking. "It's clear we could both use an ally. And Rider is a good complement to your Archer, don't you think? So… do you want an alliance, or not?"
Rin chewed her bottom lip. She had been pondering such a thing herself, actually. Forging alliances was common practice in the Grail War, and she had been hoping that a Master she knew would pop up. She would have preferred someone like Emiya, honestly… stupid and dependable. Alas, he was not a Master, having been dragged out of the country before the War even started, by Fujimura-sensei seeking a partner in her two-month-long tour of the Cheeses of Europe. She had been planning it for weeks, and everyone in school knew that when Taiga got focused on cheese, there was no real arguing with her. Shirou would be gone until long after the war ended, and would likely weigh a few extra pounds when he got back.
"Ummm… well, I would like an alliance with Rider. That's good. It's just…" Rin said.
Just that Rider comes with you attached. Like buying a new purse that is totally perfect, except it comes with a dead rat inside. Rin thought. Out loud, she said. "Just… things…"
Shinji blinked in confusion. "What kinds of things?"
"Oh… you know… the things that… happen…" Rin said. She stared very intently at her shoes. "Yeah, I don't think this is gonna work."
"… but you just said that Rider would be a good ally."
"She would be. Rider definitely would be." Rin agreed firmly. "Just… y'know…"
Rin smiled. "Good! Glad you understand. Now, I need to go… cook, or something, so…"
Rin. Archer whispered into her mind. Are you sure about this? It might help us a lot to get someone on our side.
Do you want Shinji on our side? Rin thought. Because I mean… look at him. He's just so… so Shinji.
He does have a painful amount of Shinjiness. Archer agreed. But a wise tactician does not throw away potentially valuable resources.
… … Shinji has value?
If you know how to look for it. Archer said. Some people are valuable because they are intelligent, or strong, or loyal. What is Shinji?
Well, he's tactless, and he's loud, and he's kinda skeezy, and honestly I cannot recall the last time he was actually right about anything. So while I'd totally like Rider around…
He's the dead rat in the purse. Archer said.
But that dead rat can be put to use too, Rin. Just ask medieval armies. Archer said.
… are you suggesting we shoot Shinji out of a catapult to spread disease? Because I can get behind that.
Not exactly. Archer thought. Just pointing out that there is some tactical use for a person who's opinion is always wrong.
Rin considered this.
"Shinji…" Rin said. "I believe a Servant has taken up shop at Ryudou Temple, which for our purposes is the ultimate fortification. If I suggested you and I launch a full-frontal assault on the Temple tonight, what would you think about it?"
Shinji nodded eagerly. "Sounds like a great plan!"
Rin smiled. "Archer, we're staying in tonight. Shinji… come with me."
It was the perfect partnership. If Rin had realized how useful Shinji could be, she would have started hanging out with him years ago. No matter the subject, his peculiar brand of anti-wisdom always helped her make a firm and confident decision.
It applied perfectly to the extensive combat of a Grail War…
"I'm sure we can defeat him!" Shinji said, his eyes locked on the imposing figure of Berserker.
Rin and Archer had already started running away before he finished the sentence.
And of course, he was a tremendous help to Rin's magecraft…
"Oh, is that your ritual circle? Looks good." Shinji said.
Without a word, Rin erased the lines and began to re-draw from scratch, taking care not to repeat the dozens of mistakes she had clearly made the first time. The spell, when completed, went off without a hitch.
And even basic, mundane decisions became so much easier with him around…
Rin picked up her umbrella, looking outside doubtfully.
"Don't bother," Shinji said confidently. "Not a cloud in the sky."
With a brilliant smile, Rin tucked the umbrella under her arm, and reached for her raincoat as well.
Archer had been so right. When you knew how to deal with him, Shinji was just about the most useful guy ever. Every house should have a Shinji; she didn't know how she'd ever lived without one. The ability to go through life absolutely sure what to do brought enormous peace of mind to her.
This Sakura thing was seriously weighing on her. The Magus in her said 'stab', and the sister in her said 'No'. So she really didn't want to make this decision at all, honestly. And now Shinji was just being so terribly uncooperative.
"Look, it's not that bad. In a way, it's a compliment." Rin said.
"How is it a compliment that you only keep me around so you can do the opposite of what my opinion is?" Shinji asked sullenly.
"It means I find you useful enough to tolerate your presence."
"… … … oh, how reassuring."
"Glad I could help!" Rin said. "Look, I'm going to the church. You… think about this. Really dig deep and consider what you want to do. And then let me know it."
"So you can do the opposite?"
"… … … saying 'nooooooo' would just be wasted breath at this point, huh?"
"Just… go away."
Rin nodded. "I'll bring my knife and wait for you to show up. Oh, and… if you had to suggest a route to the church, would you say I should walk down Main street, or take a turn up 30th?"
"Fine, fine! Geez, touchy." Rin muttered, walking away.
Shinji sighed, sitting down on the bench to think.
The world seemed to grow mildly colder, then. Not a harsh chill, but the light touch of a cool winter's night, when you can see your breath shimmer in the moonlight. The girl seemed to not so much walk as glide, drift like a flake of snow in the moonlight. She seemed somehow both more and less than human; impossibly beautiful and ephemeral as a fairy. As if moonlight shining against new-fallen snow had somehow been given human form.
Her large, serious eyes fixed on him, the perfect young lady spoke.
"Ewwww." Ilya said, her nose wrinkling in disgust at the sight of Shinji. Then she walked away.
"Why are all the women I know bitches?" Shinji snapped.
Shinji walked into the church, seeing Rin sitting silently by the Priest who had served as her mentor and guardian.
Kirei took one look at Shinji, and said, "Ah. You. Well… I have to go… bless something."
"Um… aren't you supposed to stay and like, make me question my morals, or…"
"Meh, your moral decisions don't really interest me." Kirei said.
"… harsh, dude."
Kirei shrugged and said, "Well, y'know… I'm Evil." Then, judging this to be sufficient reason for any action he took, he went off to do whatever it was evil priests did in their spare time between evil plots. Crochet, maybe.
"So…" Rin said, "Have you considered?" Her hands held the knife, ready to throw it aside if Shinji asked her not to.
"I think… that it's really insulting you're putting this on me." Shinji said. "And that you seem to think my only value is in my ability to be wrong."
Rin's eyes widened. "You have other value?"
"See? See, that's what I mean!" Shinji said. "Well, screw you. I'm not gonna be your bitch anymore!"
"Eeeew, no, bitch implies sexual contact. Use something else, like 'tool' or 'patsy'." Rin said, her nose crinkling.
"And stop being disgusted by me!"
"Stop being disgusting."
"Gaaaaaaaaaaaaaaaaaaaaaaaaaah! For the love of God! I have been nothing but pleasant these last few weeks! What have I done to earn this treatment?" Shinji snapped.
Kirei poked his head back into the room. "Well, when I examined Sakura, I found a lot of signs of both extreme physical and sexual abuse. Those are mostly done by relatives, so… I mean, that's a 50% chance it was you."
There was a long, somewhat dark silence.
"Seems like that would be something that would upset people." Kirei said. Then, his trolling complete, he went back to his unknown activities. Perhaps he was making soufflé. Lots of people like soufflé.
Rin stared at Shinji, and very carefully did not say anything.
"In my defense," Shinji said. "I was not going to ever tell you about that."
Sakura opened her eyes, blinking the sleep away. The smiling face of her sister looked down on her.
"I'm right here. Rider is waiting for you outside. Everything is going to be okay." Rin said reassuringly.
"Oh… and where is… Nii-san?" Sakura asked.
"Oh, he and I… had a discussion. About certain treatments of you over the past few years. It really opened my eyes, made me re-assess my priorities. I owe him a lot." Rin said.
"… that was not really an answer…"
"Well, after our talk, I asked if he thought it was a good idea for me to shatter every bone in his body and leave him with the rough physical capacity of a turnip." Rin said. "And you know? He thought it was!So I helped him out."
"…" Sakura said.
"He looked surprised, I admit. Like he expected me to… I dunno, do the opposite of what he suggested." Rin said, smiling.
"But luckily, I respected him far too much for that."