Alliance of Inconvenience
Later that evening...
(Shirou)
"Master, there's a few things we should discuss before Rin arrives later," Shirou's Servant commented once they had entered the Emiya house and closed the door behind them. Besides the dress she had bought with Rin, and some other clothes that Shirou had helped her pick up, Sasaku was also carrying some groceries. Shirou had more of the same, all in preparation for a rather large gathering.
"Sure," he replied easily while sorting out the various ingredients he would use that night. "I assume this means it's important enough to be keep secret." She simply nodded.
"Well, a few things. First of all, so you know, under some conditions, thanks to the ((Higher Connection)) skill, I actually net gain rather than lose magical energy." Shirou nodded, not really seeing the significance of this. "Basically, Kuro for example is constantly needing to draw energy from Tohsaka. As a new magus, your mana generation is hardly greater than that of a normal human. Normally, this would greatly affect your Servant's ability to do anything."
He realized what she was getting at. "So basically, anyone can keep you for free is what you mean."
She nodded while lifting another bag of groceries effortlessly. He thanked her and looked inside - it was the fish for dinner. "As you can imagine, it's possible to take other people's servants. It would not be wise to tempt Tohsaka, or any magus really, with the possibility to have a second servant."
Shirou didn't comment on that, honestly it seemed like he lucked out on his Servant. "So how much do you actually generate though?"
"Net, about equal to two decent human magi, at its peak. Not very much compared to say, trying to draw from one of the leylines or so on - which I can't do due to the exact skill that causes this - but I, uh..." Sasaku paused awkwardly.
"Your Noble Phantasm, right? Does it use a lot of energy, unlike Lancer's Gae Bolg?"
"About that, er... you see... I sort of don't really have one," she muttered sheepishly. Shirou just stared at his Servant while she fidgeted under his gaze.
"I thought Heroic Spirits have to have one, by definition. You yourself told me so."
"So, so, you see, the Grail screwed me over." Sasaku sighed with a depressed expression. "If you knew how to check, what shows up in that section is something called ((Realm Marble: Kingdom of Flowers)) which transposes the area onto the mentioned Kingdom of Flowers."
"What's that?" Shirou paused, sensing an important bit of information.
"You could say it's the crystallization of my Authority, though that's backwards. It also doesn't matter, since it exists back where I came from, which is so far away I can't get there, even after giving up my current body, without the use of something like the Grail."
"I see, so it doesn't do anything."
"Well, actually... this house is sort of my Realm now, but sadly that isn't the way it works. Either way, it's best if you just kept quiet about it. Ah, if someone was able to see just the rank, it would show up at EX though, since it's a really weird phenomenon."
"I guess. So were those the main items?" Shirou resumed his work, shifting to dinner preparation since everything else had been neatly put away.
"There's one more thing, but you might need to ask Tohsaka for more help. Sorry."
"Yeah? Out with it." Taiga had actually suggested trying to bribe Tohsaka with food. Which all things considered was probably the safest option.
"After careful observations, I've found that my ((Higher Connection)) is greatly affected by various conditions. In short, it would probably be best if I accompanied you in a physical rather than spirit form."
"Oh, is that it? Tohsaka, did you hear that?" Shirou could tell that Rin had arrived by the sense of her Servant entering his house. Or rather, Sasaku sensing it and passing on the information.
(Rin)
She had paused just after letting herself into Shirou's house, thanks to the smell of fish being fried. Until the owner of the house suddenly addressed her.
"Yeah," she muttered as Kuro appeared, already halfway to the kitchen. "It's not a bad idea, there doesn't seem to be any other Masters around school. And-" she glanced at Sasaku who was working over some vegetables with a knife, "I guess you can probably wear some of my older uniforms."
"He meant the paperwork needed," Sasaku frowned as Rin made it quite clear she still wanted to play dress-up with her. "Or do they not care much who enters school here?"
"As long as you pay the fees, pretty much," Rin simply shrugged. "It isn't as though, what, fifteen year old girls are some sort of serious threat." Kuro laughed, interrupting Rin who glared before continuing. "You don't have any guardian though, that would be a problem, unless..."
"I'm sure Taiga will oblige," Shirou said confidently.
"By the way," Rin added, remembering something else. "Your father's will does in fact say simply 'my child' in case you were wondering."
"Huh. I wonder why they never showed up. The real one, I mean." Shirou frowned while flipping over the fish to check the underside. It went onto a plate with some fresh leafy vegetables. "You didn't change that or anything did you?"
"Hmm? No, I didn't. I have no clue either, had my contacts look but found nothing," Rin lied smoothly. Actually, there were some odd rumors around the Fourth Grail War, but the Einzburns run a tight ship.
"I wonder if Kiritsugu was a magus," Shirou mused innocently, not noticing Rin's sudden grimace. "No wait, it should be my biological parents that would have been." He was distracted by the sight of Kuro trying to filch some fish, only to be intercepted by Sasaku.
"Kuro, can you quickly get back home and bring back several sets of my school clothes?" The Servant turned to give Rin a disapproving look, but Rin continued anyway. "It's best for me to not be repeatedly traveling around at night. It's in the same wardrobe as what I usually wear, but they're all the way in the back. I'm sure Emiya-kun won't be done before you return."
000============
(Taiga)
"Shirou, is that dinner? You better not have started without me!" Taiga announced as she stepped into the Emiya house. Shirou just laughed and pointed at the table, which had been set awaiting the arrival of the night's food. Taking the hint easily, Taiga sat down, pouring herself some tea after noting the number of cups and plates set out. Herself, Shirou, Sasaku and...
"Fujimura-sensei?" Rin appeared from one of the rooms down the side corridor, with Sasaku in tow. "Ta-da!" she beamed, pushing Sasaku into the living room ahead of her so everyone present could see.
"Are you already planning on going to school here?" Taiga simply asked in response to seeing the familiar uniform, though she was already wondering if this was Sasaku's idea or Shirou's.
"Shirou-nii said that if I would be staying for a while it was necessary," the girl replied with disarming demureness. "Then Tohsaka-san said 'at least you don't have any language issues' and then... it turned out like this."
Taiga thew a smile over at Shirou. Though it was probably Tohsaka who had thought up such a thing, if they were both working together. Why was another question though.
"If even Tohsaka-chan thinks you can jump right in then there's no problems. Leave it to this reliable sensei to get everything sorted out!" she said proudly.
Who just laughed?
(Sasaku)
"Um, let me quickly change back..." Sasaku tried to get back to her room, but was stopped by a smiling Rin.
"No way, there's no time for that," the bright expression on her face only made the sharp corners of her mouth stand out even more by contrast. "You wouldn't make sensei wait for dinner, right?~"
Sasaku frowned while allowing Rin to pull her over to a chair. Does she think I can't tell that Kuro is searching my room? Not that it mattered much, since almost anything could be and was stored in her ((Realm's Armory)), but it was the principle of the matter.
I'm not even sure what she's expecting to find in a Servant's room in the first place, well there's the clothes we bought earlier.
(After dinner)
Sasaku watched the two women praise their host's skills. Shirou's cooking was even better than last night's. He must have put in extra effort knowing that both Rin and Taiga would be visiting. She understood well the pride of a craftsman at work.
"Shirou-nii," she asked suddenly in the middle of their cleaning up. "Where are your textbooks? I want to read them." "Work with me here, I need to get into your room. Now."
"They're all on the table in my room," her Master replied easily. "Don't make a mess."
"Do you need some help?" Rin suddenly was on her feet and chased Sasaku. "I'm the top stude-" Both of them paused as Sasaku opened the door to Shirou's room to show it was empty, before stepping in.
"You might as well come out," the Servant said, glaring at Rin as Archer appeared next to her. "Explain what you were doing in Master and my rooms."
Kuro just looked at her in amazement. "How?"
"Are you kidding me?" Rin appeared upset, though it could easily be a ruse.
"I was in spirit form..." Kuro muttered before adding "I was only looking."
The two Servants ended up sharing Rin's frustrated glare. Kuro abruptly disappeared as the door opened behind them, though only Shirou entered. "Ok, what's going on here?"
Sasaku only replied flatly, "Tohsaka's Archer was looking at our rooms."
"I didn't ask her to," Rin grumbled. "For some reason she's gotten attached to you and I don't know why either."
"That's a terrible excuse." Shirou's disappointed look seemed to affect Rin more than Sasaku's anger had. "But you already know I'm barely a magus, there's nothing here to spy on."
"Well I knew that already!" Rin stomped out to cover her retreat. Shirou just turned to Sasaku and shrugged. "Is that all?"
"No, I actually want to read those textbooks.
(Rin)
Sitting opposite Shirou's Servant, Rin fumed at the stupidity of her own - there were limits to curiosity, and as Shirou had correctly pointed out, he had no Mysteries anyway. She herself had checked him and his place a few times. Part of the responsibilities as Second Owner.
Then again, she had also known he wasn't a magus since he was only adopted by the deceased Emiya. But then again... she had been right in that he had no magecraft ability, even if the Grail had decided he could be a Master. Bah.
Sasaku was wearing the white and blue dress from earlier in the day. It wasn't clear if she wanted to show it off to Taiga, Shirou, or just remind Rin of the whole embarrassing incident. Worse than that though, was seeing her top student status possibly get demolished.
It's a Servant, it doesn't count she repeated to herself while watching Sasaku flip through Shirou's textbooks. And frowning in disappointment.
"I can explain anything you need help with," she said helpfully, noticing Taiga's silent amazement.
"You said you're the top student? How far behind is Shirou-nii?" Sasaku asked while putting down the math book after only glancing at it. She picked up another one. "And where are we at in this?"
"Are you not good with math?" Taiga broke her silence.
"Math is universal," Sasaku replied, looking at the spot Rin indicated. "I only wondered what we were covering at this point. Now this varies by location." It was a history textbook.
"Suddenly, Shirou-kun has such a reliable younger sister," Taiga muttered from the depths of her growing depression.
"I just happen to have a habit of reading everything I come across," Sasaku said absently, switching books. "And I hardly forget anything I've read, is all." Taiga sat up suddenly, remembering the potential dangers posed by Kiritsugu's inheritance papers.
(Shirou)
After Taiga had left in a tizzy, Rin just continued watching as his Servant finished reading the books she had brought out. "Shirou, do you keep all the other books from previous years?"
"Yeah, some are also in my room, but others are probably in one of the storage rooms," he said. "Tohsaka, are you planning on dessert before leaving?"
"Sure, sounds great," the other magus replied. "Kuro will take me back later. No dessert for her."
"Aww, Master~" the immediately-appearing Archer whined. "It was purely innocent." Rin just scowled at her.
.
Notes:
Some more plot. I actually think under Grand Order rules Sasaku's Realm's Armory would be her Noble Phantasm as it can be used to attack (details on the restrictions when it's shown), while Thousand Layered Shields would be a party defense buff skill. Higher Connection would probably be like Dante's self-NP charge skill (it's the best analog I can think of) - but she has nothing like Independent Action, unless "burn mana for anything" counts.
It's fun to mess with Rin. Sasaku actually enjoys dress-up, she just doesn't care to indulge Rin.