The Yorifis estate was located deep within a forest on the outskirts of London.
Every week, Shirou was allowed to return there.
Because he always behaved obediently—timid, quiet, always buried in books in his room or the library—the Yorifis family had grown lenient in their surveillance of him.
Perhaps they believed that a cowardly little boy like him would never dare try to escape.
And Shirou had made sure to maintain that illusion perfectly.
To them, he seemed like an ideal ward—eager to study magecraft, someone with great potential who would surely serve the Yorifis family well in the future.
Little did they know…
> "You kidnapped me, and you're going to regret it for generations."
Shirou smirked inwardly.
---
That night, as the estate fell into silence and its inhabitants sank into sleep, the grand mansion wrapped in its noble history became eerily quiet.
Shirou suppressed every trace of his presence and slipped out into the forest beyond the estate.
He wasn't escaping.
Not yet.
Over the past week, his progress had been massive.
Now was the time to test it.
Of course, he couldn't afford to expose his true power—neither to the Yorifis family nor the Clock Tower.
He knew how ancient and dangerous the Clock Tower was—who knew what kinds of terrifying figures lurked within?
Tonight was his opportunity.
Once he had gotten far enough away from the estate, his magic circuits lit up all at once, mana surging through his body like a flood.
His speed exploded, his movement becoming inhuman.
As a Lesser Grail, his mana reserves were virtually limitless.
He began channeling it through a specific circuit formation.
A glow gathered in his hand—
A silver longsword took shape.
> "Is this… Projection?"
He murmured to himself.
Technically, it was magecraft Projection, but his version was fundamentally different. It wasn't just imitation or creation—it couldn't even be called true magecraft.
It was closer to a low-tier version of Unlimited Blade Works—the start of Imaginary Manifestation.
---
In the next moment, his entire body flared with energy.
A black battle outfit appeared on him, traced with glowing red lines.
Crimson markings, like glowing runes, spread across his skin and face like tattoos.
A wave of dark red sludge, molten and seething like lava, spread from under his feet—mana boiling off him in a terrifying aura.
He radiated the presence of something not of this world—as if he had just crawled out of hell.
All the Evils of This World began to stir within him, trying to twist his mind.
But they were instantly crushed—easily suppressed.
This was the result of his wish to the Grail—to have full control over his body and soul.
Not even Angra Mainyu could influence him now.
---
Blackened Mode.
This was his corrupted state—a form born from the Grail's dark magic, overflowing with power.
The tainted mud spread over a wide area, capable of engulfing enemies and absorbing their mana into the Grail's reservoir.
Then Shirou struck.
He swung his sword forward—
And in an instant, an explosion of mana surged out.
> BOOM!
The earth in front of him split apart.
Ancient trees were shredded by the shockwave.
> "That…"
Shirou stood in shock.
Even he hadn't expected this level of destructive power.
Unfortunately, he still didn't know how to activate Unlimited Blade Works.
> "Wait… is this Mana Burst?"
A realization struck him.
Artoria Pendragon (Saber) possessed the skill Mana Burst.
When corrupted, she gained an infinite mana supply, and her strength soared—enough to overpower the demigod Berserker Heracles.
In contrast, Berserker's power didn't change much after being corrupted.
This suggested that Mana Burst played a massive role in enhancing power when mana was unlimited.
Mana Burst was essentially a self-buff—enhancing strength, speed, durability based on the amount of mana output.
> "I… I can use Mana Burst? Is it something my circuits naturally have, or was it given to me after the corrupted Grail reshaped my body?"
He couldn't help but speak aloud in disbelief.
To have Mana Burst—
To be a Lesser Grail—
To wield infinite mana—
Even he had no idea how strong he could become.
Eventually, the sludge receded back into his body, and the enhanced state faded.
---
In just one week, Shirou had mastered the basics:
How to use his mana
How to activate and control his magic circuits
How to tap into the corrupted Grail's power
He was, without question, a genius.
---
Meanwhile… in Fuyuki City
Preparations for the Fourth Holy Grail War were already underway.
The Holy Grail War occurred roughly every sixty years, when the ley lines beneath Fuyuki accumulated enough spiritual energy to summon the Grail.
At that point, a Grail capable of granting any wish would descend.
Seven magi would be chosen by the Grail as Masters.
Using holy relics, they would summon Servants—also known as Heroic Spirits.
Heroic Spirits were the crystallized legends and ideals of heroes who had died and ascended into myth.
Some had formed contracts with the world while alive, agreeing to become Heroic Spirits after death.
But there was only one Grail.
So the unspoken rule was this:
> Seven Masters. Seven Servants.
They must battle to the death.
Only one pair can win.
Fallen Servants would have their souls absorbed by the Lesser Grail.
If either the Master or the Servant died, the entire pair was considered eliminated.
While Heroic Spirits were near-invincible legends, Masters were just humans—fragile and easy to kill.
If the Master died, no matter how strong their Servant was, they lost.
Once a magus was chosen as a Master, they would receive the "mark" of the Grail—a Command Seal—and would begin preparing for their summoning ritual.
Seats for the Holy Grail War were first come, first served.
Once seven Servants were summoned, all remaining candidates would be locked out.
Each successful summoner would receive three Command Seals, powered by the Greater Grail.
Command Seals weren't just tools for control—they were incredibly versatile sources of power.
---
The Ally of Justice – Kiritsugu Emiya
One participant must be mentioned here: Kiritsugu Emiya, the so-called "Ally of Justice."
In order to fulfill his dream of saving everyone, he had married into the Einzbern family, hoping to use the Holy Grail to make his wish come true.
To the outside world, he was known as the Magus Killer.
A master of modern tactics and a rare breed of magus, Kiritsugu operated differently.
Here we must distinguish:
A magus uses magecraft but doesn't care about the metaphysical Root.
A magician seeks the Root, the ultimate source of all magic.
Kiritsugu was a magus, but his understanding of magi and his ruthless methods made him feared.
He did what no proper magus would dare—hunting other magi without mercy.
His tactics were reviled.
He was an outcast from the Mage's Association.
Despite his desire to love and save the world, he was also willing to kill anyone necessary to achieve it.
He had no hesitation in his heart—
But he still felt sorrow.
Because no matter how far he fell, he was still human.
He could never discard that last piece of his soul.