Mana surged.
A scorching gale suddenly swept across the battlefield.
"Ex..."
Saber Alter gripped the inverted holy sword with both hands, and the black energy spilling from it swallowed up all the surrounding light.
The curse-laden magical energy wrapped around the blade was far too heavy and dense. Even with her power greatly enhanced, Saber Alter still could not raise the holy sword overhead, instead taking a charging stance with both hands held below her waist.
Floating before her was Lady Avalon.
Realizing that destroying that suspicious woman would break this strange space, Saber Alter ignored the threat behind her and chose to unleash her Noble Phantasm at once.
Blazing black flames became a pillar of pitch-black aurora, rising within the world of swords.
After being blackened, Saber's speed had dropped, but the time she needed to prepare her Noble Phantasm had barely changed.
It was only a fraction of a second, but that was already enough time for Shirou, closing in from behind, to land a devastating blow.
Lady Avalon had already deployed a defensive magic circle, but both she and Shirou knew perfectly well that something like that could never stand against the holy sword.
What should he do?
Should he move to shield Lady Avalon from the attack, or seize this once-in-a-lifetime chance to grievously wound Saber in a single strike?
For Shirou, that was never really a question.
But he was still behind Saber. How was he supposed to cross dozens of meters in a straight line in an instant and move onto the path of Saber's Noble Phantasm?
"..."
Shirou took a deep breath.
At the same time, Saber Alter coldly spoke the true name of destruction.
"...calibur Morgan!"
With an upward slash from low to high, she unleashed an evil dragon's breath powerful enough to pierce the sky.
Time seemed to stop in that instant.
As Shirou roared out a certain forbidden incantation, a torrent of magical energy surged through him, accompanied by the agony of his circuits being torn apart as it ravaged his body.
"Time Alter. Triple Accel!!"
Time Alter.
Originally, this was a magecraft unique to the Assassin Heroic Spirit Emiya, a technique that deployed a Reality Marble within one's own body.
Within that smallest possible bounded space, it adjusted a few fleeting seconds of time, forcibly accelerating blood flow, the burning of hemoglobin, and the time required for muscle movement from beginning to end by one to several times.
The Dead Count Shapeshifter's Command Spell that Lady Avalon had prepared for Shirou operated on the same principle. It was essentially a magical version of Time Alter that accelerated the time inside the body directly to ten years in the future.
Compared to the magecraft used by Kayneth and Tokiomi Tohsaka, Kiritsugu's magecraft had neither flashy effects nor overwhelming power.
But Shirou liked it very much.
So, old man... I'm borrowing your magecraft.
"..."
Saber Alter, having just released her Noble Phantasm, felt a gust of wind brush past her ear.
Out of the corner of her eye, she saw Shirou race past her at an unbelievable speed, then leap into the air.
"Master!"
"Leave it to me!"
Forcing himself to change direction in midair, Shirou moved in front of Lady Avalon, faced the torrent of black aurora head-on, and thrust out his right hand.
Projection Magecraft.
This was the field Shirou excelled at most.
This was the craft he had honed through endless tempering.
Much as he hated to admit it, with the body he had now, even if he drew Ea, he still could not overpower Saber Alter's firepower. The gap in the wielder's raw abilities was simply too great.
But Shirou's strength had never been about superior numbers.
He did not possess an ancient bloodline, Morgan's brilliant mind, or Melusine's overwhelming power.
And yet, the one who had ultimately unified Britain was Shirou.
Shirou's greatest strength... was that he possessed an infinite number of Noble Phantasms.
"Trace, on."
Search. Select. Analyze. Project.
There had to be a Noble Phantasm capable of standing against the holy sword. He had simply forgotten its name.
So remember it.
The Shirou of now had lost his memories as a transmigrator, so he had no knowledge of the Noble Phantasm called Rho Aias, The Seven Rings that Cover the Burning Heavens.
Otherwise, with a bit of luck, he might have been able to stop this blow, though it would have cost him his right arm.
But Shirou had no memory of that Noble Phantasm right now.
Even so, he was absolutely certain that a Noble Phantasm capable of opposing Excalibur, and one he could Project, did exist.
It existed within his own mind.
In a single instant, thousands upon thousands of swords flashed through Shirou's mind.
Then he noticed it.
"I am the bone of my sword."
The boy whispered.
Projection Magecraft was completed in an instant.
Amid the deadly torrent of the inverted holy sword, the projected Noble Phantasm was unleashed.
What Shirou projected was the strongest defense within his knowledge, a Noble Phantasm even stronger than the holy sword of the star.
"Avalon, The Everdistant Utopia!!"
The instant he roared its true name, golden starlight enveloped Shirou, and that noble fantasy took form.
"...!!"
Both Saber Alter and Lady Avalon widened their eyes at the sight.
The scabbard of the holy sword released beautiful ripples like a wall of aurora, deflecting every bit of the reversed aurora that would have burned all things away.
That was not defense, but absolute separation.
An invisible wall that kept the filth of the outside world from entering the faerie land, a world cut off from this one, forever unreachable.
Protected by the scabbard of the holy sword, Shirou, for that one instant, was severed from every truth of this world.
The strongest protection in existence, untouched even by the Five True Magics, the absolute ultimate that no one could violate.
That was why the scabbard bore the name Avalon, The Everdistant Utopia.
The utopia King Arthur could finally reach before death, the ideal land dreamt of by other kings yet forever beyond their grasp.
"..."
Gazing at that familiar golden scabbard, Saber Alter's cold expression turned dazed for a single moment.
The so-called holy sword of the star was, in truth, a device that amplified magical energy. Only Artoria, with the dragon furnace buried within her chest, could draw out its full power.
But that did not mean others could not use it.
While she was alive, Artoria had once lent the holy sword of the star to Gawain.
But the scabbard was different.
According to legend, Avalon was a place only King Arthur could reach.
In the same way, the scabbard was a weapon only King Arthur could use.
And now, at last, Artoria could confirm a single fact.
Shirou, so you really are King Arthur after all.
The immense Mana released surged outward like a flood.
Once the pitch-black aurora completely faded, Shirou and Lady Avalon returned to the ground.
"Are you okay, Master? That was way too reckless!"
Lady Avalon cried out anxiously.
Shirou shook his head and took a guarded stance as he looked at Saber Alter not far away.
Mana had once again been poured into the demonic sword in her hand.
Is she going to fire Excalibur again!?
Shirou was not sure he could use the scabbard a second time.
The scabbard had acknowledged him just now, but that did not mean it would go just as smoothly again.
More importantly, he could never win by doing nothing but defending.
"..."
The instant his eyes met Saber Alter's, Shirou made up his mind.
"Avalon-nee-san."
"Hm?"
"That's enough. Get some rest. Leave the rest of this fight to me."
Lady Avalon froze for a moment at his sudden words.
"What are you talking about? There's no way you can beat Saber by yourself, right? Besides, didn't we agree we'd win this fight together?"
"Maybe that's true, but..."
Shirou turned to her with a bright smile.
"If I can't defeat Saber on my own, then none of this means anything."
"..."
So that's what this is...
After a brief silence, Lady Avalon nodded.
[My Arthur], you really do still want to settle this with her, don't you?
"Understood. Be careful."
Lady Avalon's beautiful figure dissolved into spirit form, and Shirou turned back toward Saber Alter.
"I know you're angry, Saber.
We promised this would be one-on-one, and yet I showed up to face you with another woman by my side.
It would be stranger if a jealous Artoria wasn't angry, but did you really have to go dark over it?"
"..."
Saber Alter kept a straight face and said nothing.
Shirou watched her reaction, then let out a sigh.
"You really do see through everything... That one truth I've been hiding all this time, you'd already figured it out, hadn't you?"
He spoke in an exceptionally calm voice.
"Just as you thought, in another world, not this one, I once called myself Arthur.
And now, it seems I've obtained the concept of Arthur."
Saber Alter's expression did not change. Baobhan Sith frowned slightly. You're Arthur too...?
"But... can someone really be called Arthur just because he was granted the Holy Sword and calls himself a knight?
Of course not... the most essential element of Arthur still hasn't been shown at all."
That's right.
The reason Arthur became the ideal king.
The reason a sage prophesied, before Arthur was even born, that he would be the savior.
It was the dragon heart beating within his chest, and the dragon blood flowing through his body.
The inhuman king. The red dragon who defeated the white dragon.
It was precisely because Shirou had once perfectly reproduced that aspect that he was acknowledged by the scabbard and obtained the concept of [King Arthur].
"Artoria Pendragon, the true King Arthur... let me show you my true form."
Grabbing his left wrist with his right hand, Shirou unleashed the final Projection Magecraft of this Holy Grail War.
"[Trace on.]"
In the next instant, a brilliant crimson radiance burst from Shirou's left arm.
Unlike a Command Spell, it carried an aura like blazing fire, like a dragon species itself.
Something appeared on the boy's left hand. A reddish-brown gauntlet engraved with a dragon crest.
[Boosted Gear - Red Dragon Emperor's Gauntlet.]
Like the [Blades of Chaos] and the others, it was a Noble Phantasm that had existed deep in Shirou's memories from the very beginning.
A gauntlet that materialized the power of a dragon. In a certain world, it seemed to be called a top-tier [Longinus].
Though only temporarily, it could grant its wielder power surpassing even Demon Kings and gods.
Every ten seconds, [Boosted Gear] doubled its user's power.
Even if that power started at only one, if it kept doubling every ten seconds, the final result would become utterly terrifying.
Ordinarily, the only things Shirou could project and use in actual combat were weapons such as blades and swords. Armor was something he could not project.
But [Boosted Gear] was a little different.
Inside the dragon gauntlet, a certain sword was hidden.
That was why Shirou was able to project it.
"Boost!"
As time passed, power burst forth from Shirou's left arm, now wrapped in the reddish-brown gauntlet.
"Boost!!"
The Sacred Gear continued to sound its voice.
With each deep growl, the power of the dragon kind flowed into Shirou's body.
"...Huh?"
Cold sweat formed on Baobhan Sith's forehead.
"Wait... that's..."
She stared fixedly at Shirou's left arm, while an intense pain struck deep inside her head. The memories she had lost because of the summoning error were returning.
At the same time, Saber Alter sensed that something was wrong. Shirou's Mana signature was increasing at an unimaginable speed.
"[Excalibur Morgan]!"
She attacked decisively, unleashing her Noble Phantasm again without the slightest hesitation.
A pillar of flame formed from reversed aurora swept straight toward him.
But Shirou was already prepared.
"Time Alter : Square Accel!"
The explosive agony made Shirou's consciousness boil. He swallowed the blood rising up his throat, slammed his foot into the ground, and hurled himself backward.
The boy flipped through the air like that, escaping the sweep of the beam while forcing more and more power out of the Red Dragon gauntlet through sheer will.
Saber Alter had not expected Shirou to become even faster. This was also the first time she had ever seen someone evade a released Holy Sword.
"Boost!!!"
"Boost!!!!"
Shirou's power doubled two more times. The force pouring from the gauntlet raced wildly through his body.
The increase in ability was not limitless. It also depended on the user's own tolerance.
With Shirou's current fragile body, that of an eight-year-old child, about seven times was nearly the limit.
With the final cry of "Boost!!," Shirou's charging was complete.
"Explosion!!"
That voice meant the power increase had stopped. It was a kind of limiter.
Once the amplification stopped, Shirou could fight for a while while maintaining that enhanced state.
How long he could use it depended on what he did during that time.
The more he moved, the more he attacked, the shorter that time became.
Shirou's stamina also affected it.
If he was already fatigued, the duration would be shorter.
So one of the keys to properly using this Sacred Gear was that Shirou could not afford to get injured.
His strength naturally increased during the doubling phase as well, but compared with stopping the increase first and then maintaining the boosted state, the Sacred Gear's power was more unstable then. If he acted carelessly, there was a risk that his physical abilities would drop back to normal.
Only when he was uninjured, with both Mana and stamina in abundant supply, could he fully bring out the power of the Red Dragon Emperor.
That was why the correct way to use the gauntlet was to build up power to a satisfactory level first, then stop the amplification, and only then enter battle.
Back in the Fairy Kingdom, Shirou had learned that through countless hard lessons.
During the Longinus amplification phase, he could not move around carelessly. He had to keep running or hide.
That had been extremely difficult for the Shirou of the past, but now he had [Time Alter].
At quadruple speed, while desperately fleeing at full power, he continuously dodged the saturation bombardment of light blasts fired by Saber Alter.
The instant the charging was complete, Shirou immediately released [Time Alter].
Useful as that Magecraft was, the burden it placed on the body was simply too great.
Adjusting his breathing, Shirou faced the girl clad in pitch-black armor.
Now, just like Artoria, he too had become a red dragon in human form.
"I'll go the distance with you, then... King of Knights."
Shirou raised his left arm, now transformed into that of a dragon kind, and pointed its sharp crimson claws straight at the black Saber's cold, stern face.
"Come on! Your favorite firepower showdown!!"
...