The first light of dawn was breaking.
In the courtyard of the Butterfly Mansion, a young boy practiced a series of punches under the early morning dew.
His movements were not particularly fast, and each strike seemed simple, almost plain. Yet, through the misty twilight, his style carried a meaning that was impossible to ignore.
Fierce, wild, relentless, commanding.
As his speed increased, the intensity of those qualities grew more obvious, more pressing, until the final strike "If I Were the Emperor" released all of that manic energy.
Boom!
A single droplet of dew, hundreds of meters above, shattered from the force. White Mukai lowered his fists and exhaled slowly.
"Are you just going to watch, or do you have something to say?"
The voice was calm, detached, and with it appeared Shinobu Kocho.
"Your form is beautiful. Perhaps you and Master Tengen would understand each other," she said softly.
"Beautiful?" White Mukai shook his head, a faint smile on his lips. "That only proves that right now, I'm just performing empty gestures."
"If I were performing true Tenbu Fist, you wouldn't find it beautiful. You'd be terrified. You'd tremble, feeling fear coil through your very core."
White Mukai admitted that he was not particularly skilled with this Tenbu killing style, a martial art and technique created by the legendary Great White Shark, Tendou. But his lack of mastery was not because he lacked detachment or resolve.
Shinobu glared at him, still unable to shake her frustration at his habit of speaking crudely. She could no longer regard him as a mere child. Yet this was not the time for trivialities.
"Our lord has responded. He wishes to meet with you," she said quietly. "But I must first go to headquarters. The Hidden will come to escort you later."
White Mukai let out a short laugh. "I don't care about your covert methods. But do you really want me treated like a 'package,' to be transported at someone else's whim?"
He understood the Demon Slayer Corps' caution, but he could not accept being treated like cargo.
"Fine, go meet your master. We'll discuss the rest later."
Before Shinobu could speak further, White Mukai waved, interrupting her. She obediently fell silent and left.
"Heh. Though this world is weak, its quirks only make it more interesting," he murmured, flexing his arms. After a violent spasm through his bones, he looked at his hands, noting the increase in size, and laughed softly.
Physical growth was necessary. The strength of the magnetic field depended not only on raw power but also on efficiency and flow. Efficiency meant using energy more effectively; flow meant regenerating magnetic power quickly.
The most intuitive measure of flow was body size. A small, weak body could not sustain large amounts of energy, while a larger frame could channel more. For the strongest, this simple logic did not hold, but for White Mukai, who had yet to even rotate his magnetic field, it was crucial.
Unfortunately, at the age-equivalent of seven, his body could not sustain enough energy flow. If he fought at full strength, his recovery could not keep up with consumption. Physical growth could not be accelerated through electricity alone, so he used other methods.
A soft rustle of wind announced a figure in the shadows behind him. White Mukai withdrew his fists and exhaled calmly.
"State your business."
"Yes, Lord Mukai," Zero knelt respectfully, her body trembling.
Demon cells were the most fascinating aspect of this world to White Mukai.
These cells had extreme regenerative and division capabilities, ignoring telomerase decay entirely. They healed rapidly, granting a form of immortality.
But there was a flaw.
Ultraviolet light became a destructive force, breaking down DNA rapidly. Without an immune system, demons could not defend against allergens, and ultraviolet exposure could destroy their genes entirely, leaving no trace.
Even this flaw alone was reason enough for White Mukai to reject the idea of becoming a demon.
More interesting to him was the principle behind Muzan Kibutsuji's control over demons. It was not a matter of willpower. By studying near-death cells of Zero, White Mukai discovered part of the secret.
Muzan controlled each demon because their cells originated from him. These cells retained a unique base sequence upon merging with the host. Activating this sequence allowed him complete control.
He even embedded a special trigger in the sequence: if the demon's subconscious spoke Muzan's name, the sequence would produce excessive amino acids, forming long protein chains that destroyed the body like a runaway cancer.
White Mukai had yet to understand how Muzan projected his will through these cells. Limited tools and his reliance on electrical stimulation only allowed him to study this far.
Still, with his current method, he could forcibly alter the base sequence of a demon's cells. Zero was a live example. It was a dangerous procedure, akin to "burning the body to purify it," and few demons could survive it.
White Mukai could not guarantee that Zero could convincingly deceive Muzan, even with part of the base sequence intact. But the fact that she had not raised suspicion meant he now had a foothold at Muzan's side.
Yet this was not the main focus of his study.
Demon cells had another remarkable trait: extreme efficiency in nutrient absorption. Humans wasted most energy from food. Magnets, on the other hand, could convert matter directly into energy.
Demon cells absorbed up to ninety percent of nutrients, meaning they could grow stronger simply by consuming humans.
However, their diet was extremely limited only humans could provide the necessary DNA. Other food was unusable. Their immortality and endless regeneration relied entirely on this efficiency. Without continuous consumption, the cells would stop dividing, and the demon would age and die.
White Mukai could only study this aspect superficially, as the principles of the "Blood Demon Art" remained beyond his understanding. Yet he could still manipulate the demon cells he controlled.
By using electrical stimulation to remove Muzan's control sequences and redirect nutrients, he could promote normal growth without cell division. In a few days, he aged the body from seven to twelve, at the cost of only a few bottles of human blood.
The taste was unpleasant, and the method seemed crude, but White Mukai dismissed such criticism. Evolution favored intelligence and adaptability. To blindly cling to pride and refuse adaptation was true foolishness.
Having grown sufficiently, White Mukai no longer needed further physical development. He destroyed the now-redundant cells and began ultimate training, blending local martial breathing techniques with his magnetic cultivation, aiming to overcome the world's limitations entirely.
"So, this is their plan," White Mukai murmured, glancing at Zero kneeling before him.
Through her, he understood Muzan's schemes: assembling his strongest subordinates, plotting to eliminate him, even using human authorities to hunt him. It was not a smart choice, but the decisiveness impressed White Mukai. He looked forward to meeting Muzan in person.
But first…
He had to deal with the Infinity Castle, the domain of the troublesome Biwa Demon, to create conditions for a fair fight with Muzan.
"In the meantime, follow Muzan's orders," White Mukai told Zero softly.
"I do not ask for loyalty or gratitude. Just do not interfere with my plan. Take care of yourself."
"Yes!" Zero knelt, her head nearly touching the ground, trembling. Though he had saved her from Muzan, White Mukai was no kind savior he was more terrifying than Muzan himself.
Her submission was due entirely to the electrical stimulation lingering in her mind. Disobedience would bring pain surpassing death.
With a wave of his hand, Zero vanished from the Butterfly Mansion. White Mukai watched Shinobu disappear, smiled faintly, and followed immediately.