Infodump, ho!
Rolled 92, 61, 87. DC 40. Three successes!
You raise your arms and speak slowly. "I subdued your associate because he attacked a friend of mine with the intent to kill. I captured him because I wanted information about what is going on. I do not want to fight if I don't have to."
The girl relaxes slightly at your words, though her expression doesn't change. "I've already stated my conditions."
You nod in understanding. Without a word, you free Styil.
The boy gets up stiffly, but gives you a smug smirk. "My rings," he demands haughtily.
If he weren't in his under clothes, he might cut an intimidating figure. But he is and you're not intimidated in the slightest. You shove the arrogant child toward his ally and he crashes at her feet.
The girl doesn't overreact to her partner's mistreatment, relieved as she is to have him back. Her eyes rest on him for only an instant before they return on you, following you as you put yourself between her and Index. "You won't hand her over."
You cross your arm and shrug. "I know very little of this situation, but what I know is that this girl has no wish to be with you and that you are willing to hurt her." The two flinch at the accusation. There is history there. "As such, I cannot step aside while you take her away. I do not wish to fight, but I will if you force me to."
Saying that, you glare at them with the full combative spirit of a warrior of countless battlefields. Their eyes widens as your pressure hit them, and they reevaluate you yet again. You're not a snake trying to slither his way out of trouble, they realize. You're a cornered tiger about to jump at their thraoat.
Even then, you don't expect the boy to back down. After how his day has turned, he must be itching for payback, regardless of the risks.
"Screw you, esper! I'm going to enjoy watching her put you in your place!"
You ignore him entirely, only interested in his partner's reaction. She's the threat, but also the one cool-headed to consider meeting you in the middle.
"Styil, enough."
"Kanzaki?" The boy says dumbfounded.
The girl puts an hand on his shoulder and speak to you. "I am Kanzaki Kaori of the Church of Necessary Evil, Necessarius."
You nod. "Emiya Shirou."
This is when Kamijou barges in, right hand held forward like a shield. He probably thought the worst after he saw the slashed door, but he calms down when he sees everyone's fine. He looks at the newcomer, his eyes lingering on her very long weapon, before turning to you. "This is the part where you tell me this is your girlfriend, right? Please?"
...Well, you can't refuse an opening like that.
"I wish," you say fornlornly, your gaze trails on the girl's body with obvious admiration.
The girl's cheeks bloom the deepest red and she fidgets nervously under your leer.
A real blushing maiden, how cute. She really is a child, utterly inexperienced, probably kept isolated by her powers and status.
But with that, the tension entirely leaves the room. As proof, Komoe claps her hands and adresses everyone with a large smile. "Alright, you may be unusual guests, but welcome anyway! Who wants a cup of tea? I have chocolate too!"
Soon, the group makes itself comfortable in the small appartment and Kanzaki tells her story.
As it turns out Index is also part of Necesarius, an underground group of enforcers for the Anglican Church. Their role is to suppress and destroy magicians who steps out of line and endangers the peace. Part of that is to keep forbidden knowledge, Grimoires, from getting in the hands of those who would misuse it.
'Magic Grimoires' refers to texts containing knowledge from another plane, knowledge which contradicts the law of the world and if mishandled would drive the reader insane. In the hand of a trained handler, that knowledge become 'magic.'
Grimoires, as in the sum of knowledge itself rather than the physical form, are eternal entities that cannot be destroyed by any means in the current world, and so they must absolutely be kept somewhere safe. That is Index's role.
Her Magic Name (And you have no idea what the hell is that supposed to be. More worrying, the two magi have no idea either.) is Dedicatus545, the lamb that guard the knowledge of the strong. She was born with photographic memory and was used by the Anglican Church to record 103,000 individual Grimoires and thus allow to destroy their previous physical form.
You have to admit, it's a brilliant move. A single woman is easier to defend and move that an entire library and all that knowledge in a single place is also an excellent bait for to draw out magi hungry for power and knowledge. Which in your experience would be any magus ever, but you suspect that the religious organization is just happy the less magi are running around. Magic is heresy, after all.
You wonder how it feels about espers.
Index carries nearly all the forbidden knowledge in the world in her mind. There is however, a price to pay.
"The brain's capacity is rather minimal," Kanzaki says mournfully, "even more so in Index's case, as she remembers everything around her, from the smell in the winds to the number of threads in the coat of a passerby. Her brain was already filled at 85% by the Grimoire, leaving her only 15% for everyday life. In her case, that 15% is only enough for one year. Any longer and her brain would be destroyed by the pressure."
She turns toward the younger girl, giving a look of affection and guilty sorrow. "That is why every year, we erase her memory. Until last year, Stiyl and I were her friends and guardians, but after she forgot she mistook us for her enemies and ran away."
The girl isn't telling you the whole truth, you feel. not lying, but carefully obscuring details. Not so surprising, considering she's giving her life story to strangers under duress.
Aside from that, there's something about this story that you feel is...
"Hum, I'm sorry, but you're not being serious, are you?" Komoe dares to ask . "I mean, you're story is kind of..." She scrunches up her face, the childish teacher looking utterly adorable as she struggles mightily to find the right word, "...stupid?"
Yeah. That.
The magi don't take it well. Their faces twist in anger and Kanzaki's hands clench on her weapon. Clearly, they're being very serious about this.
Kamijou jumps in before things turn sour. "Don't take it the wrong way! She's a teacher in the city of Science. She can't take story about magic seriously."
"I'm sorry!" The tiny woman wails from behind Kamijou's back, close to tears. "Kamijou-chan is right, but this isn't about magic. It's just, Index-chan having only one year's worth of memory space doesn't make sense!"
Styil growls. "You're calling us liars? you little...!"
"I'm sorry!"
"Wait! Listen to her. The brain is a key part of an esper's power. She may not be a neurologist, but Komoe-sensei has to know a lot about it mechanism for her job. Please, listen to what she has to say."
Styil looks at Kanzaki, who nods. He settles down grudgingly. "Please," she says.
Suddenly on the spot, Komoe takes a deep breath before switching into what you assume is her lecturing mode. "Well, I only know some basic neurology, but it's enough to tell you the brain definitely doesn't work the way you think." She starts counting on her fingers. "First, memory isn't one big bag where everything is throw in, but several separates sections meant to stored different things. Everyday memories and knowledge picked from books aren't even in the same category so one can't affect the other. Second, eidetic memory is a known, documented condition and the people who had it lived long, full lives. They certainly didn't die before reaching their tenth birthday, so even if Index-chan had only 15% left, that's much more than one year worth of space."
"Finally, brain don't explode because there's too much data in it!" She declares firmly, shaking her head repeatedly. "I don't care about magic books or anything like that, that's just completely, positively, entirely iiiiiiiiiiiiiiimpossible!"
"But," Styil starts, absolutely stunned. "It does happen. Every year at the exact same date, Index brain starts to break down. We have to erase her memories or she'll die. If it's not because there's too much of them, then what?"
"Isn't it obvious," Kamijou throws in. "Your higher ups want to be sure they can control Index, right? What better way than to make sure she stays a blank slate in need of someone holding her hand?"
How about erasing her memory once and then properly build her personality so that she became entirely devoted to the church and their cause? The yearly memory erasure seems to be overkill, really, unless they think Index will inevitably slips out of their control if given enough time. You keep those speculation to yourself, as they're entirely based on your gut feeling.
Kanzaki look shaken to the core by Kamijyou's spiel. She gets up shakily. "This is...I need to talk with my superiors."
"They may just lie to you again," you warn.
Kanzaki's eyes grow cold. "No, they won't." She says with finality. "We'll leave Index in your care for now."
With that, the two magi leave.
As she needs the rest, Komoe is willing to let Index sleep in her home. Kamijou wishes to stay, fearing that the magi might come back.
As for you:
[]You stay. Can't be too careful
[]You leave. Kanzaki can be trusted.
-[]You're kinda hungry. Buy something on the way home.
--[]Go straight home.