Fuyuki City awoke in the pale light of dawn, oblivious to what had just happened.
In a humble room, a young man with red hair and amber eyes stared at himself in the mirror in disbelief. Emiya Shirou ran his fingers over his youthful face, as if by touching his skin he could convince himself that this wasn't a dream. But no matter how much he blinked, the image remained the same.
He was a stranger inside his own body.
Until recently, he had been just an ordinary otaku, an aimless guy who spent his nights watching anime and drinking sugary sodas, without a care in the world. But in a cruel twist of fate, his life had abruptly ended. Now, his consciousness had awakened in the body of Emiya Shirou, long before he was adopted by Kiritsugu Emiya.
With a shaky sigh, he muttered to himself,
"If my old self is dead... then from now on, I am Emiya Shirou."
But the shudder in his voice didn't go unnoticed. It wasn't just the shock of being in another world. Something in his body felt different.
It was then that he noticed what he held in his left hand. Opening his palm, he saw a golden shard, shining and imposing, resting on his skin. But before he could even wonder where it had come from, the gold began to melt as if it had a will of its own.
An instant later, black mud—dark, thick, malignant—seeped from the molten gold and began to slide over his skin. The substance had a weight that didn't belong to this world, a deep corruption that clung to him as if it wanted to devour him.
Shirou barely had time to react before the mud engulfed him completely.
In that moment, his mind raced, processing a flood of memories. The Third Holy Grail War, the sin of the Einzbern family, the failed summoning of Angra Mainyu, the evil spirit who was nothing more than an ordinary man condemned by his people. His existence had been devoured by the Holy Grail, and in his desperation, the Grail itself had granted his wish without any asking.
The corruption began then.
The Great Holy Grail, which was meant to be the link between the world and the Throne of Heroes, was corrupted.
And now, Shirou Emiya was its new vessel.
A suffocating pain spread through his body. The corruption of the Holy Grail wasn't simply trying to change him. It wanted to consume him.
"Is this how... I'm going to die?"
Chaotic thoughts crossed his mind as he struggled to hold on to himself, resisting the influence that sought to replace him with another self, a blackened version of his existence.
And then, the world changed.
He found himself in a blank, empty yet imposing space. Right in the center, a large golden cup floated. The structure of the Holy Grail was majestic, with patterns etched into its surface that reflected an ancient, divine power.
It was the True Holy Grail.
Shirou felt its significance with every fiber of his being. This was no mere artifact. It was a mechanism capable of granting any wish.
If the Holy Grail could grant miracles, then…
"I want complete control over my body and soul!"
The golden cup burst into light. In that instant, Emiya Shirou achieved the impossible: he rejected Angra Mainyu's influence and kept his will intact.
However, the power was too much. His Magic Circuits began to expand uncontrollably, as if his body were trying to adapt to an energy it was never meant to receive.
The pain hit him again, deeper, more violent. As if every cell within him was being dismembered and rebuilt from the ground up.
Before he could even scream, darkness claimed him.
Miles away, the sudden burst of power did not go unnoticed.
The three great magical families of Fuyuki—the Einzbern, the Matou, and the Tōhsaka—felt the great magical explosion resulting from the clash between All Evil in the World and the Holy Grail.
Unbeknownst to him, Emiya Shirou had become the new epicenter of the Holy Grail War.
The morning light filtering through the window slowly woke him.
His body was still drenched in darkness, but the black mud now sank inside him, hiding inside like a parasite waiting for the right moment.
When he finally opened his eyes, he realized that the world around him had changed. He no longer saw things as he had before. Now he could feel magic, its constant flow in every corner of the air.
"Why did I see the Holy Grail...? Was it the True Holy Grail...?" Why did I have a fragment in my hand...?
The questions hit him one after another. But what worried him most was his survival.
Until recently, he had believed he could avoid the Holy Grail War, stay out of it, and live a quiet life. But now he realized he had no choice.
As the bearer of the Corrupted Grail, he would be drawn into the conflict no matter how hard he tried to flee.
Perhaps it was his destiny…
But he must survive. And if he had the power to change those tragedies he knew so well, he would do anything to alter the course of events.
His blood boiled with that conviction.
Until a cold thought struck him.
It wasn't the regular Servants or the magi of Fuyuki who posed the true threat.
The real obstacle was Gilgamesh, King of Heroes and the former king of Uruk.
The possessor of the King's Treasure, the one who had in his arsenal countless weapons, both sacred and demonic, and of divine nature, capable of extinguishing any enemy before they could react.
The Golden King who wielded the Sword of Rupture, Ea, the Noble Phantasm capable of cleaving the world with its absolute power.
Shirou closed his eyes.
He was not the real Emiya Shirou.
He wasn't sure if he possessed the Reality Sphere (固有結界, Koyū Kekkai, literally: Innate Bounded Field) Unlimited Blade Works in this body.
He only knew that he must become stronger.
If he wanted to survive… he had to find his own way.
"No, perhaps I'm not completely without hope!"
The words escaped Emiya Shirou's lips with fierce determination, almost like a suppressed scream from the depths of his soul.
His body had changed. He was the Corrupted Grail, its bearer and vessel, but his wish had allowed him complete control of his body and soul. The corruption hadn't consumed him, not as it should have.
Somehow, the Grail's will and his own had converged into a single entity, allowing him to wield dominion over its power without being swallowed up by it.
There was still hope.
He couldn't understand why the Holy Grail had appeared in his hand or why his existence had been altered in this way, but what he did know was that he now had a chance to change fate.
"At what point in time am I...?"
He looked around, trying to get his bearings. If his memory was correct, he was around seven years old. The Fourth Holy Grail War hadn't even begun yet.
Tōhsaka Rin had been born the same year as him. Illyasviel von Einzbern was a year older.
Matou Sakura was a year younger than Rin. Which meant she was now six years old.
And that...
That meant he could still do something.
His jaw clenched, his heart pounded. No, he must change certain tragedies.
For example, Sakura!
The rules of magical bloodlines were cruel. Only one descendant could inherit the family's magical seals.
The magic seal was more than a hereditary symbol. It was an auxiliary engine of the Magic Circuits, an artifact engraved with arcane knowledge that allowed one to access power without the need for chanting.
Tōhsaka Tokiomi, the head of the family, had decided that his heir would be Rin.
Sakura, the youngest daughter, was sent to the Matou family.
But the Matou were no longer the honorable magi family they had once been. Over the centuries, their Magic Circuits had degraded to the point of near extinction, and desperation drove them to adopt inhumane methods to sustain their lineage.
Matou Zouken, the patriarch, was an existence closer to a corpse than a magi. A being who desperately clung to immortality, corrupted by his own desire to attain the Holy Grail.
With Matou Kariya's departure, the Matou family had no suitable candidate to compete in the Fourth Holy Grail War.
Zouken made his decision. He would train Sakura as his tool for the Fifth Holy Grail War.
And "training" under the Matou family was… worse than death.
To "adapt" Sakura to the Matou heritage, she was thrown into the Worm Pit, the lair of those loathsome creatures, and part of the now Matou Zouken.
Under the guise of "education," the girl was subjected to endless torture.
Children have fragile hearts. When despair becomes too great, they cannot endure. They don't understand life well enough to cling to it.
Sakura didn't even have a real notion of what hope or dignity meant.
The Worms were Zouken's familiars, magical parasites designed to feed on the host's life energy and convert it into magical power.
In a sense, they were similar to Magic Circuits.
But they weren't a gift, but a curse.
They ripped open their victims' insides, caused unimaginable pain, and when the host exhausted their magical power, they devoured them whole.
And Zouken hadn't placed one or two inside Sakura.
He had filled her body completely.
Every day, every hour, every second... she suffered.
To save her, Matou Kariya did the unthinkable.
He returned to the Matou family, sold his life, and became a Master in the Fourth Holy Grail War.
The deal was simple: "If I obtain the Holy Grail... Sakura will be freed."
But it was too late.
Despair had already consumed Sakura.
For her, hope was poison.
Because if she saw a light... she could no longer bear the darkness.
For Kariya, she couldn't know he was trying to save her. His sacrifice had to be silent, because if Sakura believed she could be rescued and failed...
Her heart would be broken forever.
But Kariya failed.
And Zouken held Sakura back.
Shirou closed his eyes, trembling with rage.
"Matou Kariya was a real man, and Matou Zouken should be torn to pieces!"
He gritted his teeth in suppressed fury.
He wouldn't allow such a tragedy to happen.
He had to change Sakura's fate!
But at that moment, his body tensed.
His skin tingled.
Waves of magical energy had appeared around him.
The Fuyuki magi had located him.
His Magic Circuits had been hidden, leaving only fifty-one detectable circuits, but that hadn't been enough.
When he became the Corrupted Grail, the magical power released was too great to go unnoticed.
He was discovered!
Shirou ran to the window and threw it open.
The normally bustling streets of Fuyuki were empty.
The magi had driven away the civilians with their incantations.
And then...
The door to the room opened.
A middle-aged figure crossed the threshold. His bearing was imposing, his dark, cruel gaze filled with calculation.
Shirou hardened his gaze.
He wasn't ready for this.
He didn't know how to fight.
He didn't know how to use the Corrupted Grail's power.
But... it didn't matter.
He would survive.
Because if there was one thing he knew for sure...
It was that he was going to change Matou Sakura's destiny.