Satsuki Kurogiri—Godword Mayday.
It is true that the abilities of my Six Paths and his own possess a certain compatibility, and it cannot be denied that he let his guard down thinking he had suppressed me… but nonetheless, he is one of the ten most powerful beings within the TYPE-MOON world.
Even Francesca Prelati, who is registered in the Throne of Heroes as a Caster, mentioned him as one of the few individuals who managed to kill her physical body. Considering that the other humans capable of slaying Francesca include the likes of Van-Fem—the 14th of the Twenty-Seven Dead Apostle Ancestors from Tsukihime—the Wizard of Parallelism Zelretch, Alice's predecessor as the Witch of Fairy Tales, and Touko Aozaki herself, one can easily surmise his true strength.
Of course, given that Francesca's specialty lies in illusions that deceive the world itself, it's possible that Godword's ability to impose world-scale common-sense alteration was simply a conceptual hard counter.
….Anyway, enough listing his broken traits. Let's consider how to recruit him.
His singularity can be summarized by two points.
First, he wields the Unified Language, a type of cognitive and world-altering ability that functions as a significantly degraded version of Marble Phantasm. Second, he is cursed by fairies.
He was a prodigy from childhood, but after being kidnapped by fairies, he slaughtered them all. This resulted in a curse that rendered him an idiot incapable of re-identifying his own memories.
Consequently, he suffers from a unique form of short-term amnesia; while he can retain information, he cannot distinguish between them. To put it plainly, he possesses memories of himself, but he cannot tell if those memories belong to him or someone else entirely.
He attempted to find records of himself within the records of the Root through the Unified Language, but such a thing was naturally impossible. Instead, he became overwhelmed by countless memories, eventually becoming a man who collects the memories of others as his sole hobby and identity.
Having completely lost his sense of self, he was unable to form a proper ego. He became a one-dimensional human who merely reacts to the situation before him, devoid of even the most basic human greed or selfishness. His attack on me was merely a counter-response to an 'enemy' invading his domain to kidnap someone; he only intended to send me back and never truly sought a fight.
Simply put, he is a harmless civilian with a mental landscape that is impossible to comprehend and a hobby that is impossible to justify.
"The problem is, this man is far too useful."
The overwhelming versatility of the Unified Language, the stability of his harmless personality… and the combat prowess to wipe the floor with Francesca.
For these reasons, I have decided to recruit him, and it is time to lay the groundwork.
"Therefore, I request that you repair his physical form and create a reserve body for him."
"Am I some kind of bottomless magic cornucopia to you…?"
Touko Aozaki looked despairing. But what could she do?
If she didn't like it, she should have made her own money.
* * * * *
A 'changeling' refers to a child left by fairies in exchange for a human child they've stolen. Of course, it is also a term for the act of kidnapping itself, often used as an excuse to abandon disabled or sickly infants.
In Satsuki Kurogiri's case, since he killed the fairies who kidnapped him, his curse was far more severe, causing his very memories to be distorted.
Based on the events of FGO Part 2 Chapter 6, a fairy's curse is typically inscribed upon the soul. This is why even Godword Mayday's Unified Language could not bypass the curse to maintain his memories. If the fairy curse engraved on the soul can be removed, he will no longer suffer from the inability to perceive his own memories. Of course, he would also be forced to abandon his malicious hobby of collecting and replaying the memories of others… but do I care?
"The body follows the soul. There is no need to create a completely new vessel; we just need to fix the body once the curse is removed."
"…You're going to remove the curse? Is your Human Path even capable of… Ah, right. You mentioned you could play around with my memories too."
"No, I won't be using the Human Path this time."
I will use a curse far more potent than any 'paltry' fairy curse—the curse of Human Evil. It is time to utilize the Naraka Path, the ultimate medical device that even temporarily sustained Zolgen after he was drenched in the mud of Angra Mainyu.
He will have to experience being chewed and ground within that darkness, but surely he can endure that much.
"Hmm. Still, I didn't expect you to be so obsessed with the Unified Language. Is it because of the Mystic Eyes of Distortion and that priest?"
"I can't deny it. The most effective way to suppress homicidal impulses is an ability that distorts perception and reality itself. A human's innate nature cannot be fixed even with the Six Paths of Reincarnation. One must control their own will."
And there was one more crucial thing I hadn't told Touko Aozaki.
'I need his help to secure cooperation from the figures on the Tsukihime side.'
Arcueid Brunestud, currently suffering after being deceived by Roa; Noel, who has the potential to fall into becoming a Dead Apostle; and Sion Eltnam, who is struggling because of her cursed lineage.
Noel, alongside Ciel, can serve as a second pipeline to the Holy Church. In Sion's case… she is a prime candidate for the next Director of the Atlas Academy. As for Arcueid… does she even need an explanation? She's a monster capable of defeating a Magician in a direct confrontation.
In any case, the Naraka Path chewed on his body for several hours before spitting him out. Touko sighed and poked at Kurogiri's body, now covered in the slime of the King of Hell, before speaking in confusion.
"Strange. There's absolutely nothing for me to fix here."
"That shouldn't be… Even if it was a curse, removing something that has been settled in the soul for so long should normally impact the physical vessel."
"Regardless, I have nothing to add to this body. If there had been a physical issue to begin with, the Clock Tower's medical staff would have swarmed him and fixed it long ago. It was because they couldn't that he fled and was placed under a Sealing Designation."
"…But that is no longer the case, I presume."
He had opened his eyes at some point, speaking with proper honorifics and clear pronunciation, quite unlike his previous self.
* * * * *
"You two have a nice chat. I'm heading out for some errands."
Perhaps wanting to avoid an awkward interrogation, Touko Aozaki quickly opened the door and fled, leaving the two of us face to face.
Just as I was about to speak, he held up a hand and spoke first.
"This-room-shall-not-be-perceived."
"…The Unified Language?"
"I would prefer not to be detected by anyone else for the time being. Now, could you explain why you have done this to me?"
"An explanation."
Yes, explaining wasn't a bad idea.
However… in this situation, there was a far better method than words.
"Why don't you see for yourself?"
"…What?"
"My eyes are connected to the Root, so it is impossible for me to directly face your Unified Language. But when it comes to memories, isn't that a different story?"
"I see. That would be faster. You don't mind?"
When I nodded, he began to replay my memories using the Unified Language.
"Guh—!!"
"…I knew that would happen."
"W-Wait. What on earth did I just see? The future… and so vividly… Explain! No, explain this to me! What does this mean? A burning city… and the extinction of humanity!?"
"Is that all you saw?"
"What… wait, are you saying that wasn't the end of it?"
"It would be faster to see it directly."
His face had turned deathly pale. He barely managed to suppress his gag reflex as he forced himself to replay the rest of the memories. Once he had confirmed the final memory, he slumped to the floor.
His hands were trembling violently, but he eventually found his voice as if shaking off the terror.
"…Is that an certain future?"
"You must have heard the news from Fuyuki City. An Evil of Humanity manifested there."
"Oh, Jewel Old Man… To think the organization intended to save humanity would instead become the worm that destroys it… And they intend to incinerate the Human Order entirely? How can such a thing be permitted…?"
"It won't be. That is why I have come for you."
To an ordinary person, simply saying 'the world will end' and providing proof isn't enough to demand cooperation.
Therefore, I had utilized various carrots and sticks. I ensured family safety for Kiritsugu Emiya, an outlet for impulses for Kotomine Kirei and Fujino Asagami, and safety and status within the Clock Tower for Waver Velvet and Kayneth El-Melloi.
Whether they had experienced it directly or indirectly, they still knew nothing of the true Evil of Humanity, Solomon. Naturally, they might have resisted my proposal to fight a life-or-death battle, whether passively or actively.
But I had also thought of something else.
If I could project the world I see, the future I know, and the scenery I behold exactly as they are—could I not convince anyone?
This was the final reason I recruited him.
"What… would you have me do?"
Once fixed, he becomes a winning lottery ticket that has already been drawn.