Chapter 10: The 'Mu' in Muzan Stands for Incompetence
The world Akira Kanzaki now inhabited was one he had only ever known through a screen in his previous life—the world of an anime, brought to terrifying life.
It was a world defined by a singular, brutal conflict: humanity's desperate war against demons.
The genesis of this nightmare began a millennium ago. The heir of the prestigious Ubuyashiki clan was struck down by a terminal illness in his youth. Just as despair began to set in, a doctor appeared, claiming to possess a cure. Yet, after several treatments, the young man's condition showed no signs of improvement. Instead, a horrifying, unnatural transformation began to twist his body, warping him into something monstrous.
In a blind rage at his worsening state, he murdered the doctor, forever halting the unfinished cure.
In the aftermath, he discovered the change was deep. He became powerful, brutal. Human food was now utterly repulsive to him, replaced by an insatiable hunger for human flesh. The constant torment of his illness had vanished, but the price was his humanity. He could have accepted this grim bargain, but then came the horrifying discovery: he could not withstand even the faintest touch of sunlight. For the proud heir of a great clan, being unable to walk in the day was a fate worse than death.
His mind, already fragile from years of suffering, finally shattered.
He learned that devouring humans made him stronger. He learned that his blood could twist others into his kin, bound to his will. He learned that neither he nor his creations would ever age or die from disease. And so, he gave these immortal beings a name—demons—and crowned himself their progenitor, their king: Muzan Kibutsuji.
With his ascension, an age of darkness began, marked by the rampage of man-eating demons.
Having attained immense power and a seemingly endless life, Muzan was consumed by a single, obsessive goal: to conquer the sun. From the notes left behind by the doctor he had slain, he learned that the final, crucial step of his treatment required a rare ingredient called the blue spider lily. If he could find it, he would become a truly perfect being, free from his only weakness.
For the next hundred years, Muzan prowled the nights, turning humans into demons with reckless abandon, commanding his ever-growing legion to search for the mythical flower.
The birth of a monster like Muzan from their bloodline brought a terrible curse upon the Ubuyashiki family. Generation after generation, the male heirs died young. It was only by marrying into a line of Shinto priests that they managed to extend their lifespans to the age of thirty, but this was an absolute, unyielding limit.
To atone for their ancestor's mistake, to lift the curse upon their family, and to save the world from the plague they had unleashed, the Ubuyashiki clan founded the Demon Slayer Corps. They vowed to fight the demons until the end of days, with the ultimate goal of destroying the Demon King himself.
In the beginning, the Corps was utterly overwhelmed.
Though the Ubuyashiki family discovered sun-drenched ore and cultivated artisans who could forge it into Nichirin Blades, humanity remained at a staggering disadvantage. Killing even the weakest demon was a monumental task. A Nichirin Blade, imbued with the power of the sun, could only eliminate a demon by severing its neck. A human body, however, had far more vulnerabilities. A demon needed only to protect its throat, while a Demon Slayer had to defend their entire body to remain in the fight. This, combined with the immense gap in physical strength, made victory a rare and costly thing.
This desperate struggle only began to turn with the appearance of one man: Tsugikuni Yoriichi.
He created the Breathing Styles, revolutionary techniques that allowed humans to push their bodies to superhuman limits, fundamentally changing the combat capabilities of the Demon Slayer Corps. Though casualties remained high, they could finally hunt demons effectively, no longer forced to rely on suicidal tactics and sheer numbers.
It was also Yoriichi who, by a twist of fate, encountered Muzan Kibutsuji. In a single, decisive battle, he inflicted a wound so deep it scarred not only Muzan's body but his very soul—a psychological trauma etched into his genetic code. The self-proclaimed invincible Demon King was so thoroughly broken that he went into hiding for over a century, and even after re-emerging, he moved with a coward's caution.
One moment of Yoriichi's bravery had bought Muzan a lifetime of fear.
During that long period of dormancy, Muzan finally began to organize his forces in earnest. It was then that he established the system of the Twelve Kizuki.
However, his idea of "organization" was laughably simplistic. He merely created the Twelve Kizuki to serve as his high-level workhorses, bestowing them with more of his blood to grant them greater power. Their orders were the same as any other demon's: find the blue spider lily and eliminate the Demon Slayer Corps.
Simultaneously, he strictly forbade his demonic subordinates from gathering in groups. This paranoia stemmed from the time he was gravely wounded by Yoriichi; in his moment of weakness, a single demon had managed to escape his control. The feeling of losing that absolute authority disgusted and terrified him. He lived in constant fear that if his demons ever united, they might find a way to break his hold and turn on their king.
From Akira's perspective, everything the Demon King did was marked by a startling lack of intellect. His strategies were crude, his thinking utterly basic.
Despite possessing immortality and overwhelming power, he never once thought to approach the true rulers of the human world—the shogunate, the powerful lords—and use their vast resources to search for the blue spider lily. Surely that would be more efficient than sending his monstrous minions scrambling through the wilderness?
After all, the fact that becoming a demon meant being enslaved to Muzan's will was a secret. If he didn't tell them, how would they know? Even the current Demon Slayer Corps was largely unaware of the exact mechanism of his control. The Ubuyashiki family itself went to great lengths to suppress all news of demons, precisely because they feared that powerful, ambitious humans might seek that power for themselves.
And that wasn't even touching upon the myriad of absurd, self-sabotaging actions Muzan took in the original story. It was no wonder that in Akira's old world, fans had a running joke: the 'Mu' in Muzan's name didn't stand for 'nothingness,' but for 'incompetence.'
This Demon King, aside from possessing strength currently unmatched by anyone, had absolutely nothing else to his name. And even that strength was a gift from a long-dead doctor; it had very little to do with Muzan himself.
'No, I can't keep thinking like this,' Akira thought, forcibly reining in his thoughts. If he continued down this path, he would start to genuinely underestimate Muzan.
No matter how incompetent or cowardly, the Muzan of this era was an invincible existence—a colossal threat to every living being, including Akira.
In fact, it wasn't just Muzan. To the current Akira, even a random, newly turned demon was a life-threatening danger.
Therefore, mastering a Breathing Style and growing stronger as quickly as possible was the only thing that mattered now. Only with sufficient power could he hope to survive in this treacherous world. Only then could he save the people whose tragic fates had filled him with so much regret in his past life.
As Akira's thoughts settled, the gentle rocking of the carriage came to a halt.
They had arrived at Momoyama.
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