The probability of victory was zero—unless I played my hidden card... No, even then, this was an opponent I couldn't defeat.
It goes without saying, but starting from the end of the Fourth Singularity, the difficulty of the Restoration of Human Order begins to skyrocket. We have the Mad King, whose Saint Graph is described as being on the level of a 'Divine Spirit'; the Goddess Rhongomyniad, who became a true 'Divine Spirit'; and the Seventh Singularity, where 'Gods' and 'Beasts' roam free.
The Fifth Singularity is the flashpoint of that escalation—a threshold that teaches you exactly how irrational and loathsome a Divine Spirit can be.
As the saying goes, Divine Spirits do not exist to be fought. Those capable of slaying such beings are restricted to Great Heroes at the literal zenith of their prime, such as Gilgamesh or Enkidu; the King of Knights wielding Avalon; or Heracles, should he be summoned in Greece in the Archer class.
Even for them, engaging a genuine Divine Spirit is a harrowing ordeal. If one were to seek those truly capable, you'd need someone like Manaka holding the Holy Grail, or perhaps Scathach, who reached the Root and half-ascended past humanity after slaughtering countless gods and wraiths. Even for Scathach, it is canon that she is pushed back when facing the Mad King.
Naturally, using a trump card against such a foe... meant having one fewer 'measure' against the unprecedented enemies of the future: the Lion King in the Sixth, Tiamat in the Seventh, or Goetia in the final chapter. To use a metaphor... yes, it was no different from juggling a line of credit. To ward off a present threat, I was putting my future life up as collateral. In many ways, it was an act even more foolish and vicious than simple debt rotation.
I had already exposed my Boundary Formula, and the Mad King was already aware of Arcueid and the Fifth Magician. Now that the Boundary Formula was compromised, even the Mastermind would be on guard... I had to find a way to escape using only my own strength, without relying on outside intervention.
"Shinra Tensei!"
"Futile."
It was going to be excruciatingly difficult.
Vicious spear thrusts rained down incessantly. Having already switched my entire body into the 'Auto-Mode' of the Asura Path, I utilized the Rinnegan's insight to evade every attack by a paper's width. I wasn't sure whether I should praise the Rinnegan's perception and the Asura Path's automation, or be terrified by the Mad King's ability to bypass them both. Because I had diverted my entire mental focus to the Asura Path, utilizing any other technique was effectively impossible.
Naturally, I didn't do something as foolish as pulling out Gae Dearg to clash spears. Before he was the Mad King, this was Cu Chulainn. Even within a Berserker's Saint Graph, his spearmanship was etched into his soul. Even if I had handled a spear a few times, trying to match him blow-for-blow would be idiocy.
Just as my right arm—morphed into a blade—shattered, and his spear, a tool of eviscerating slaughter, was about to pierce my heart, a stone I had embedded near my teeth flew out, glowing with an explosive light. The Primordial Rune—the Sun Rune, crafted with the aid of Touko Aozaki—released a blinding flash. The Mad King's response was characteristically simple.
"Useless."
A single swing.
The moment he swung his spear, I felt the sensation of blood rushing to my feet, like the G-force of a rollercoaster. It took only a fraction of a second to realize the truth: I wasn't the one flying away. The ground itself had been deeply hollowed out, and I was falling into the abyss.
"There!"
The Mad King did not miss that window. Thrusting his spear with blinding speed, he skewered my heart and hoisted me up with a triumphant shout, reversing his grip as if holding a harpoon thrown by a fisherman...
"...Self-destruct!"
"...What? It wasn't the real—!"
Simultaneously, my Asura Path 'puppet' detonated.
It was a form of Substitution Ninjutsu achieved by utilizing the 'Order Change' function integrated into my Chaldea Combat Uniform. I had hesitated to use such a risky, unpolished technique against a Heroic Spirit, but in this situation, I had to throw everything I had into the fray, no matter how clumsy.
Moving via the interference of Ryougi Shiki or Manaka Sajyou was off the table as I'd already used that card. My main combat force, including Arcueid, was stationed at the Fuyuki Singularity and couldn't be summoned... I had to face this alone.
And then, a thorn from his spear burrowed through the earth where I was suppressing my presence.
In a panic, I released a repulsive force, flipping the entire terrain and hurling it at him. In response, a fist the size of a pot lid slammed into my jaw. I attempted to form a prana receiver in my palm to embed it in his forearm, but my hand was broken instead. The Spear of Slaughter surged toward my eyes once more.
"Shinra Tensei!"
"Oh, right. That trick is useful. But if that's all you've got, this is starting to get boring!"
"Ha... to think you're paying more attention to me than other legendary Heroic Spirits is quite the honor... But compared to them, I'm really nothing special, you know?"
"Don't make me laugh. You ran from Ulster, ran from me to Alcatraz, and hid your face for weeks. You call that a hero? Hardly. A hero is one prepared to fight bravely and die... Fine, I'll complete you as a hero right now."
"Screw you!"
The Mad King was executing the kind of deceptive tag-team pressure Fionn mac Cumhaill and Diarmuid used to display—entirely on his own. One attack would force the cooldown of Shinra Tensei, while the next strike would pierce the opening. Because his parameters were so monstrously high, every strike had to be blocked regardless of whether it was a feint or a killing blow. His attack speed was so absurd that the cooldown for Shinra Tensei couldn't keep up. The version of Shinra Tensei that creates a shroud around the body was out of the question; it would simply be shredded...
"Full Power Shinra Tensei!!!"
The same full-throttle repulsion Pain had used to level the Hidden Leaf Village.
It's a known fact that the smaller the point of impact, the greater the force. A car can drive over a bed of hundreds of nails safely, yet a single fixed nail will puncture a tire instantly.
I condensed and compressed the repulsive force, then hurled it directly at his stomach. I felt my shoulder shatter under the pressure of his spear, but it didn't matter. Before the spear's curse could reach my heart, I could purge the limb via the Asura Path and replace it with a mechanical arm. Long live the Rinnegan cheat code.
"Fly all the way to the end of America!"
Boom!
With a thunderous roar, his hardened muscles caved in as he was pushed back. A split second later, a violent shockwave of repulsion erupted, blasting him away with extreme force.
"Cu-chan!"
"Naraka Path Manifestation!"
Naturally, I couldn't stop here.
Among the Six Paths techniques, the most powerful required significant casting time. Aside from the near-instantaneous Shinra Tensei, the Mad King would never give me the breathing room to chant techniques that consumed vast amounts of prana. I had to do it now. After all, what idiot would stand there with their eyes open while someone cast Chibaku Tensei?
"Altera! Grab the Naraka Path and run!"
"Acknowledged."
"...Damn it, stop them! Those bastards are fleeing a duel...!"
"Don't make me laugh! Take this—Buster Call!!!!"
My arm swelled.
It bloated, grew, and expanded until it formed a massive construct.
A weapon of destruction that looked down upon the 'Little Boy' and 'Fat Man' dropped on Japan, and indeed every weapon of mass destruction ever produced by man... a modern 'Noble Phantasm' was brought into existence.
"I know Servants are incredibly tough. But no matter how strong you lot are, I doubt you can survive a destructive force that rivals Karna's Vasavi Shakti."
The Tsar Bomba—the Emperor's Wrath—manifested in its purest form.
Thunder, ominous light, and then, the explosion.
A level of destruction that could easily suppress the Noble Phantasm of almost any Heroic Spirit bloomed before them. I manifested the King of Hell and quickly dived inside. Carrying it away was Altera's job... and she would remain intact even if she were spun inside a particle accelerator. That was the nature of Impure World Resurrection...
Clutching the mouth of the King of Hell with her arm, her body was torn apart by the aftershocks of the blast as she was forcibly propelled by the shockwave. Before long, she was tossed haphazardly onto a desert area where a massive mushroom cloud was clearly visible... Naturally, having regenerated in an instant, she picked up the Naraka Path and set it upright so I could emerge.
Even though the space inside the Naraka Path was a distorted dimension completely isolated from the outside, I was ultimately the master of that domain. Monitoring the situation outside was no issue... and when I felt the blast subside after a few minutes, I quickly exited the King of Hell.
No matter how fast Altera was, she was ultimately slower than the Motored Cuirassier.
As I emerged, Altera seemed to realize the situation and prepared to jump on the back instead of into the sidecar, while I pulled out the Motorcycle Mystic Code.
"...Ugh!"
At that exact moment... the spear carrying an incurable curse lodged itself in my arm. I severed the limb instantly and remanifested it, but... yes, I could feel it in my gut. I couldn't run.
"Ah, you shouldn't use such boring tricks to run away at the end... Well, perhaps the problem was that I evaluated you as a warrior? Still, as a commander, your strategy was quite admirable..."
From now on, I will kill you as a King.
The Mad King gave a wicked laugh, gesturing with his thumb down as if declaring those words... The enemy Servants were all intact. The Mad King... his face was slightly scorched, but it didn't seem like a significant blow.
That's right—that crazy King took the Tsar Bomba head-on and blocked the entire explosion with just his spear... Damn it, human, is it really okay for his output to be this broken?
"...Master, go. I will stop him here."
"It's no use. If you stay, he'll just hunt me down once he's done with you... Ha, this is driving me insane."
Since Altera didn't have a conventional life, using the standard soul-extraction methods was impossible... But if I used the card meant for Goetia here, I would end up dying in the Final Singularity...
In this situation, the only thing I could do...
"Altera."
"?"
"No matter what it takes, even if your body is ground to dust, hold him. Can you do it?"
"Acknowledged."
Toward the four Heroic Spirits and the single King, the Great King of Destruction—her skin cracking and her eyes turned pitch-black—charged.
As if he had been holding back until now just to match my pace, the Mad King began to run wild. He didn't care if his body broke; instead, he treated his own injuries as a resource to crush them all. When his arm holding the spinning Photon Ray was severed, he picked up the severed limb with his other hand to swing it. When his legs were cut, he used one arm to vault himself and flew via Prana Burst to pierce an archer's arm. Even when his head was blown off, he caught it like a bowling ball and hurled it.
"How tiresome."
However, that desperate struggle ultimately meant nothing.
Even though she would regenerate so long as she wasn't completely pulverized, regeneration required time, and the Mad King exploited that. He smashed, crushed, and broke her again and again. Until the Impure World Resurrection was canceled, she would regenerate infinitely, but his strategy was cruel: he severed every limb and the neck, giving her absolutely no window to counterattack.
...The time he took to do that was barely forty seconds. A precious, fleeting interval.
And then, he looked at me.
"Yes, this is enough. Now, die."
"...Not so fast... Fine, I have no choice but to step back for now...!"
The Spear of Slaughter was leveled at me, and I pulled out the final trump card I had held back until the very end... Much like how I had summoned the Boundary Formula in the Third Singularity, this was a strategy of robbing Peter to pay Paul—a self-destructive move in the long run. But if I didn't use it, I would die.
The small card, a mix of purple and black, depicted a dignified elderly man of mature age. I gripped the card, which contained the essence of the Second Magic, and prepared to channel prana.
The Second Magic, which draws upon the possibilities of parallel worlds. It wasn't enough to one-shot this madman and scream, 'It's over, Fifth Singularity cleared!' but it was enough to extricate me from this situation. It was the Second Magic, after all—an ability that allowed me to tap into an infinite number of parallel possibilities, even if only in a limited capacity.
...Yes, if it had functioned properly, that's how it should have gone.
[Ah, you're finally here! The Junior of the Root Zelretch mentioned!]
At that exact moment, a colossal lock manifested, blocking the Spear of Slaughter that was hurtling toward me.
...What?