"Ngh... aaaaagh!"
Violent pain swept through Sakura Matou's entire body in an instant.
It felt as though countless red-hot needles were searing her nerves all at once.
She let out an anguished wail, her body convulsing violently, almost collapsing to the floor.
"Don't move."
Seiji Fujiwara's voice stayed calm, but it carried a command that brooked no argument.
His other hand braced the girl's shoulder, holding her in place.
The pain lasted a full ten minutes.
For Sakura, those ten minutes were longer than the past ten years.
But just when she felt she was about to be torn apart by the pain, the agony receded like a retreating tide, swift and sudden.
In its place came a warm, comfortable feeling she'd never known before.
She could clearly sense that the worms gnawing at her flesh and mind day and night had, for the first time, fallen into "slumber."
That torment which had plagued her for ten years, present every waking moment, vanished for the first time.
"...It doesn't hurt."
She murmured to herself and slowly opened her eyes.
Two streams of clear tears slid silently down her pale cheeks.
They were tears mingled with joy and release.
"How do you feel?" Seiji withdrew his hand and asked with a smile.
"It's... it feels good." Sakura looked at him, those purple eyes filled with gratitude and fervent attachment.
In her eyes, the man before her was no longer a "doctor."
He was the "god" who had saved her from hell.
"This is only the first step." Seiji said gently. "To cure it completely will take several more treatments. In the meantime, don't tell anyone, including your... grandfather."
"Mm!" Sakura nodded hard.
Seiji watched her hang on his every word, dependent and obedient, and inside he felt nothing but cold indifference.
His so-called "purification," of course, was not done out of kindness.
He'd merely used his higher-tier power to temporarily "paralyze" those Crest Worms.
At the same time, during the process, he had quietly left a "mental backdoor" belonging to himself alone on the core of those worms, the enormous mother worm linked to Zouken Matou's main body.
Bit by bit, he was stealing supreme control over this "perfect vessel" out of Zouken Matou's hands.
"Well then, I should be going."
Having accomplished his purpose, Seiji didn't intend to linger.
He turned, preparing to leave.
"Um... Mr. Fujiwara!"
Sakura suddenly mustered her courage and called out to him.
"Next time... when will you come again?"
There was a note of pleading and attachment in her voice that even she didn't notice.
Seiji looked back at the girl's expectant eyes and gave her a reassuring smile.
"Soon."
"Believe me, Miss Sakura."
"Soon, I'll bring you out of this hell completely."
With that, his figure vanished into the shadows beyond the door.
Leaving Sakura alone, standing in the empty room, turning over and over in her mind that promise he'd left behind, one that sounded like a divine oracle.
...
...
After the battle with Berserker, the fragile alliance entered a brief period of calm. Everyone understood that until they found an effective way to deal with Heracles, any rash move would only be self-destructive.
But the chessboard of the Holy Grail War would not stop turning just because one side had stalled.
That afternoon, Waver and Rin Tohsaka were in the Workshop of Tohsaka Manor, arguing over the formula and ratios for a new type of alchemical explosive, trying to develop a weapon that could break through the defense of "God Hand."
Shirou Emiya was off to one side, clumsily practicing the "Reinforcement" magecraft, trying to make his strength count for at least a little something.
Seiji, as usual, played his "support" role, preparing tea and snacks and providing data support for everyone.
Just then, an unexpected "visitor" shattered this false calm.
"...High-density magical reaction detected, approaching fast!"
The defensive barrier of Tohsaka Manor suddenly let out a piercing alarm.
"Who is it?!" Rin's expression changed, and she rushed to the crystal ball used for surveillance.
In the crystal ball's image, a woman wearing a deep-purple cloak, its hood concealing most of her face, hovered quietly outside the front gate of Tohsaka Manor.
Beneath her feet there was no flying device of any kind; she simply floated in midair, defying the laws of physics.
"Caster..." Waver's face turned grave. "And a Caster who knows flight, an Age of Gods magecraft!"
"What does she want? Is she going to attack our base directly?" Rin nervously gripped the jewel pendant hanging at her chest.
"No, doesn't look like it." Seiji had been calmly watching the screen, and he spoke up. "She hasn't shown any hostility, and the barrier hasn't detected any offensive spells. She seems more like she's... waiting."
"Waiting?"
"Yes, waiting for our invitation."
Sure enough, the moment Seiji finished speaking, an ethereal, elegant female voice rang directly in everyone's minds through magical communication.
"...A pleasure to meet you, Masters of Saber and Archer. And you as well, esteemed Overseer from the Clock Tower."
"My name is Medea. As you can see, I am a Servant who has descended into this world under the Caster Class."
"I come with no ill intent. I merely wish to invite all of you to my Workshop, Ryuudou Temple, for a friendly discussion."
"A discussion?" Rin frowned. "A Caster, inviting hostile Masters to her own Workshop? That's a weasel wishing the chickens a happy new year, no good intentions at all!"
"It is suspicious." Waver agreed. "A Caster is nearly invincible inside her own Workshop. If we go, we're walking right into the trap."
"But, sensei, Miss Tohsaka," Seiji spoke again, offering a different view, "have you considered why she dares to do this?"
"Why?"
"Because she has nothing to fear." A glimmer of wisdom shone in Seiji's eyes. "She knows full well that we've just crossed swords with Berserker and understand his strength. And as the Caster who occupies the Spiritual Vein hub of Ryuudou Temple, her own power is likely no less than Berserker's."
"In that situation, by flexing her muscles and extending an invitation, she's actually sending us a message. She doesn't want us as enemies, and may even... want to ally with us."
"Ally with a Caster?" Rin's expression was full of contempt. "Servants of the Caster Class have always been the ones who love betrayal and scheming most. Allying with her is like negotiating with a tiger for its skin."
"But a tiger can sometimes be put to use," Seiji said with a smile. "At least, when facing a lion."
He pointed at the map, at the enormous red cross marking Berserker.
"Having one more powerful ally to fight Berserker together is no bad thing for us. And besides... going to the meeting doesn't necessarily put us at a disadvantage."
"Oh? You have a plan?" Waver asked at once.
Seiji walked over to Rin and said respectfully, "Miss Tohsaka, your Archer has the Independent Action ability, doesn't he?"
Rin nodded. It was the high-tier skill unique to the Archer Class.
"Then we can do this." Seiji spoke unhurriedly, but with clear logic. "You and Emiya, with Saber, go to Ryuudou Temple as our representatives for the meeting. I'll accompany sensei and provide technical support from the rear."
"And Mr. Archer can use his Independent Action advantage. While we draw Caster's attention from the front, he can quietly slip into the mountain behind Ryuudou Temple and investigate that place's... true secret."
"The location of the Greater Grail..." Waver's eyes lit up.
It was a plan to kill two birds with one stone.
It could both feel out Caster's true intentions and depth, and seize the chance to investigate the most central Secret of the Holy Grail War.
"...All right, let's do it that way."
In the end, Rin was won over by this bold and meticulous plan.
...
An hour later.
Ryuudou Temple, before the mountain gate.
Saber escorted Rin and Shirou as they slowly climbed the long stone steps.
The ancient temple looked solemn and dignified in the afterglow of the setting sun, but the air was thick with a magical energy so dense it nearly took physical form.
Saber could feel that the entire mountain was shrouded by an immense barrier.
Here, Caster's power would be amplified to a terrifying degree.
That witch named Medea was waiting quietly before the temple's main hall.
"Welcome, my guests." She lifted her hood, revealing a face of stunning, fairy-like beauty. A trace of elegant amusement showed in her eyes.
"Please, come in. I've prepared tea and refreshments for all of you."
And in the mountain behind Ryuudou Temple, where they couldn't see.
The red-clad Archer moved like a phantom, weaving soundlessly through the dense forest.
His target was the enormous hollow hidden within the mountain itself, the place where the Greater Grail lay.
...
Inside Ryuudou Temple's main hall, sandalwood smoke curled upward, yet the atmosphere was cold as frozen frost.
Medea, this legendary princess of Colchis, the great magus of the Age of Gods, displayed a poise that was elegant and composed, utterly different from the "witch" of legend.
She personally poured black tea for Rin and Shirou, every gesture carrying the nobility unique to royalty.
"There's no need to be so tense, young lady of the Tohsaka family." Medea said with a smile, her voice ethereal and pleasant. "As I said, I bear no ill will. I simply want to make a deal with you."
"A deal?" Rin held her teacup but didn't drink, her eyes full of wariness. "What is there for us to deal over?"
"Plenty." Medea's gaze swept over Saber, who had stayed in a combat stance off to the side and hadn't said a word. "I know who your enemy is. That undying monster, Berserker, correct?"
"I can help you deal with him."
"Oh?" Rin raised an eyebrow. "And the terms?"
"Quite simple." Medea extended one slender finger. "Once Berserker is dealt with, I need you to help me deal with my Master."
"Deal with your Master?" Shirou exclaimed in surprise. "You... you want to betray your Master?"
"Betray?"
Hearing the word, a self-mocking smile crossed Medea's face. "A man who from the very start never treated me as a Servant, only as a Mana Battery and a tool, is he even worthy of speaking of loyalty?"
A flash of deep, bone-cutting hatred passed through her eyes.
"He is not a qualified Master. He isn't even... a qualified human being. He's just a base creature, hiding in the dark corners, toying with power and scheming."
Though she didn't say it outright, everyone present guessed who she meant.
A Master who could make a Caster hate and dread him so much, who else could it be but that mysterious, unidentified original owner of Ryuudou Temple?
"So, you want to use us to win your freedom?" Rin cut straight to her purpose.
"You could put it that way." Medea admitted frankly. "It's a deal beneficial to both sides. Isn't it?"
The hall fell into a brief silence.
Rin and Shirou were both thinking fast.
The proposal was full of temptation, but equally full of risk.
...
Just as the negotiation inside the hall reached a stalemate.
The mountain behind Ryuudou Temple.
Archer had successfully avoided all the warning runes and familiars, slipping to the entrance of that enormous cavern within the mountain, the "Dragon's Cave."
A magical energy so vast it was suffocating rushed out at him from deep within the cave.
That energy was pure and ancient, as if it were the most primal life force of this planet.
"So this is... where the Greater Grail lies?"
A grave expression came over Archer's face.
He was about to investigate deeper.
Then, abruptly, a lazy voice came from a tree behind him.
"Hey, you over there. Archer."
"What are you doing skulking around in my backyard?"
Archer's pupils contracted sharply. He turned at his fastest speed and put distance between them.
A man in a blue bodysuit, with long blue hair, a crimson spear resting on his shoulder, leaned at an angle against a tree, watching him with a half-smile.
His gaze was sharp as a spear tip, brimming with a beast-like, battle-hungry air.
"You're... Lancer?!" For the first time, shock showed on Archer's face. "Didn't I... already kill you?"
"Ah, that." The blue lancer scratched his head and said indifferently, "It's just that my useless Master got killed off by your Master, that's all. I've been resummoned by a new Master."
"By the way," he leveled the red spear from his shoulder at Archer, a bloodthirsty smile spreading across his face, "my new Master is a real interesting fellow."
"The first order he gave me was..."
"...to kill any thief who dares come near this place!"
Before the words had finished.
His figure turned into a streak of blue lightning, instantly breaking the sound barrier, the red spear in his hand howling as it tore through the air, stabbing straight for Archer's heart!
Gáe Bolg!
The cursed spear of reversed causality!
The moment the spear thrust out, the "effect" of "piercing the heart" was already predestined!
...
"...Alarm! High-intensity Noble Phantasm reaction detected in the rear mountain!"
Inside the command vehicle, the screen before Seiji turned a glaring red in an instant.
"What?!" Waver and Rin cried out at the same time.