The idea came to Kenjaku during a sleepless night, three months into his intensive training regimen.
He had been reviewing his accumulated knowledge, cataloging the techniques and abilities that existed across both source materials that composed this merged world. Shinobi techniques from Naruto. Jujutsu abilities from his original existence. The hybrid developments that emerged from their combination.
And then he remembered Cursed Speech.
The Inumaki clan's inherited technique—the ability to infuse words with cursed energy, compelling reality itself to obey spoken commands. In the original Jujutsu Kaisen timeline, Inumaki Toge had used the ability to devastating effect, forcing opponents to stop, run, explode, or sleep through nothing but his voice.
The technique had limitations, of course. Using it strained the throat, caused backlash proportional to the command's difficulty, and could fail against opponents with significantly superior cursed energy. But the core principle was sound.
Words as weapons. Commands as attacks. Reality reshaped through speech.
And Kenjaku had Idle Transfiguration.
He could modify his own soul, reshape his own existence, add capabilities that he hadn't been born with. If he could understand the spiritual mechanics that made Cursed Speech function, he could theoretically integrate those mechanics into his own being.
The Inumaki clan didn't exist yet—or if they did, they were obscure enough that he hadn't encountered references to them. But that didn't matter. Kenjaku didn't need to find practitioners of Cursed Speech. He needed to understand the principle well enough to recreate it.
And he was very, very good at understanding principles.
The research began immediately.
Kenjaku started by analyzing the relationship between cursed energy and verbal expression. When sorcerers spoke during combat, their words carried emotional weight—threats, declarations, technique names. That emotional weight generated cursed energy, which flowed through the vocalization.
Normally, this energy dissipated uselessly. Words were just sounds, after all. They didn't have inherent power to affect reality.
But what if the energy didn't dissipate?
What if it was shaped, focused, compressed into a form that reality couldn't ignore?
The Uzumaki sealing tradition provided a framework. Their techniques used symbols to encode intent, creating patterns that spiritual energy was forced to obey. Spoken words were just another type of symbol—auditory rather than visual, temporary rather than permanent, but fundamentally similar in function.
If Kenjaku could develop a method of encoding intent into speech the same way the Uzumaki encoded it into written seals, he could create a verbal equivalent of fuinjutsu.
Cursed Speech through first principles.
The experimentation was methodical, as all of Kenjaku's work was.
First, he modified his throat and vocal cords using Idle Transfiguration, creating structures that could channel cursed energy through sound production. The modifications were delicate, requiring precision that pushed his technique to its limits.
Second, he developed a meditation practice focused on imbuing words with intent, training himself to compress emotional weight into verbal expression rather than allowing it to scatter.
Third, he tested the results on progressively more challenging subjects, starting with insects and small animals before moving to human targets.
The failures were numerous and occasionally spectacular.
His first attempt at a command—"Stop"—produced nothing but a slightly echoing word that made his test subject look at him with confusion. The cursed energy had been present but unfocused, lacking the structure needed to compel obedience.
His second attempt produced a backlash that left him unable to speak for three days, his modified vocal cords rebelling against the unnatural strain he'd placed on them.
His third attempt killed the test subject instantly, the command "Sleep" interpreted by the poorly focused energy as "Die" and executed with lethal efficiency.
But failure was just data. And data led to refinement.
By the end of the second week, Kenjaku had achieved basic functionality. His commands worked—not with the reliability of a true Inumaki, but well enough to be useful. Simple instructions like "Stop," "Run," and "Fall" could be delivered with reasonable success rates against ordinary opponents.
More complex commands remained problematic. The backlash increased exponentially with command complexity, limiting his practical vocabulary to single words or short phrases. And the technique consumed far more cursed energy than it should have, suggesting inefficiencies in his implementation that would require further refinement.
But the foundation was established.
Kenjaku had successfully integrated a new inherited technique into his own existence.
And that meant he could do it again.
"Master, your voice sounds different," Hana observed one morning, her enhanced perception detecting the subtle changes in his vocal production.
"I've made modifications." Kenjaku tested his throat with a few experimental sounds, feeling the cursed energy channels respond smoothly. "My speech now carries... additional weight."
"What kind of weight?"
Rather than explain, Kenjaku demonstrated.
"Kneel."
The word hit Hana like a physical blow, cursed energy compressing into a command that her soul couldn't refuse. Her legs buckled immediately, dropping her to her knees despite no conscious decision to do so.
The effect lasted only a moment before her own spiritual defenses reasserted themselves, but the demonstration was clear.
"That's..." Hana stared up at him with wide eyes, her devotion somehow deepening despite—or perhaps because of—the violation she had just experienced. "You can control people with words now?"
"To a limited extent. The technique has significant costs and constraints." Kenjaku helped her stand, his touch clinical. "But yes. Another tool for the arsenal."
Hana's expression shifted through several emotions before settling on something that looked disturbingly like arousal. The idea that her master could command her absolutely, could override her will with a single word, clearly appealed to whatever remained of her independent psychology.
Kenjaku noted this response and filed it away for future consideration. Her obsession had reached levels that were becoming increasingly difficult to manage productively.
But that was a problem for later.
Right now, he had more integrations to develop.
The next logical step was combining Cursed Speech with his existing techniques.
Maximum: Uzumaki was his primary offensive ability—a concentrated blast of cursed energy drawn from his collected spirits and enhanced by Uzumaki sealing principles. The technique was already formidable, but it lacked versatility. It was pure destruction, useful only for overwhelming force.
What if he could add commands to the attack?
The theory was straightforward: embed Cursed Speech into the energy projection, creating a blast that both damaged and controlled its targets. A Maximum: Uzumaki enhanced with "Burn" would not only strike opponents but compel their bodies to combust from within. One enhanced with "Shatter" would fragment flesh and bone beyond normal damage parameters.
The implementation was considerably more complex.
Combining techniques required understanding how they interacted at a fundamental level. Cursed Speech operated through auditory channels, requiring the target to hear the command. Maximum: Uzumaki was a visual phenomenon, a beam of energy that struck before sound could travel.
The mismatch seemed insurmountable until Kenjaku realized he was thinking too literally.
Cursed Speech didn't actually require hearing in the physical sense. The Inumaki clan's technique worked through spiritual compulsion, using sound as a delivery mechanism but not actually dependent on the physical vibration of air molecules.
What if he could encode the command into the energy itself?
The breakthrough came after three days of continuous experimentation.
By infusing his Maximum: Uzumaki with the same spiritual structures that made Cursed Speech function, Kenjaku created a hybrid attack that delivered commands directly to the target's soul upon impact. The sound component became unnecessary—the technique simply communicated its intent through the medium of destructive cursed energy.
He called the result Maximum: Uzumaki - Voice of Ruin.
The first test obliterated a small hillside.
Kenjaku had aimed at a rock formation, embedding the command "Disperse" into his attack. The energy beam struck the stones and, rather than simply shattering them through force, caused the entire formation to explosively decompose at the molecular level. The rocks didn't break—they ceased to exist as coherent matter, their fundamental structure convinced to abandon itself.
The second test was against a captured bandit.
"Die," Kenjaku commanded through his enhanced Maximum: Uzumaki.
The bandit died. Not from the energy damage, which he might have survived for a few agonizing seconds. But from the command itself, his soul accepting the instruction and simply... stopping. His heart ceased. His brain halted. His existence ended with a completeness that ordinary death couldn't match.
There was no resistance. No suffering. No drama.
Just absolute, irrefutable termination.
Kenjaku smiled his distinctive smile.
Now this was progress.
The integration with Idle Transfiguration proved even more interesting.
Normally, Idle Transfiguration required physical contact for significant modifications. Kenjaku could make minor changes at range, but anything substantial needed direct soul-to-soul interaction through touch.
Cursed Speech offered a potential workaround.
If commands could be delivered through sound—or through the spiritual equivalent that his modified technique used—then commands to transform should be possible as well.
"Reshape," Kenjaku instructed his next test subject, infusing the word with both Cursed Speech compulsion and Idle Transfiguration intent.
The subject's face melted.
Not metaphorically. The man's facial features literally rearranged themselves, responding to the command as if Kenjaku's hands were molding them directly. Nose, eyes, mouth—all shifted position, creating a configuration that should have been impossible but now simply was.
The effect was unstable. Without direct contact to provide precise guidance, the transformation was imprecise, more destructive than creative. But the principle was proven.
Kenjaku could now modify souls at range through verbal command.
The implications were staggering.
In combat, he could reshape opponents without touching them. Lengthen their limbs at inopportune moments. Seal their senses. Transform their bodies into configurations that couldn't support life.
With preparation, he could affect multiple targets simultaneously, commanding transformations across an entire battlefield.
With refinement, he might be able to make the effects permanent, embedding transformation commands that would persist indefinitely.
The technique needed more development. The cursed energy costs were extreme—each combined command drained reserves that would have powered dozens of normal techniques. The precision was lacking, making targeted modifications difficult compared to direct contact.
But as a weapon of mass effect, it was already devastating.
Kenjaku had created something entirely new. Something that combined jujutsu principles, shinobi sealing methods, and his own unique capabilities into an ability that no one in either source material had ever possessed.
He was becoming something beyond categorization.
Something unprecedented.
Something terrifying.
The Domain Expansion test required extensive preparation.
Domain Expansion was the pinnacle of jujutsu technique—a manifestation of the user's innate domain, a space where their will became absolute law. Within their domain, a sorcerer's techniques became guaranteed hits, their power maximized, their control complete.
Kenjaku had possessed a Domain Expansion in his original existence, though he had rarely used it. The technique was costly in cursed energy and revealed his capabilities to anyone who witnessed it. He preferred subtlety over spectacle.
But this wasn't his original existence. This was a new world, with new opportunities and new threats. And the domain he had possessed before might not manifest the same way through his current body.
He needed to test it. To understand what his domain had become.
The testing ground was a deserted valley far from Uzushio Island, a place so remote that no one would witness what was about to happen. Kenjaku had traveled for three days to reach this location, leaving Hana behind to maintain his cover at the Uzumaki village.
Alone in the wilderness, surrounded by nothing but rocks and dead trees, he prepared to manifest his inner world.
The technique began with the standard hand sign, though the gesture was more psychological anchor than actual requirement. Kenjaku closed his eyes, centered his consciousness, and reached for the core of his existence.
Domain Expansion was, ultimately, an expression of self. The domain's nature reflected the user's psychology, their philosophy, their understanding of their own technique. Mahito's Chimera Shadow Garden had manifested as a dark space filled with distorted hands, representing his view of souls as clay to be molded.
Kenjaku's self-understanding had changed since his merger with Marcus Chen. He was no longer simply an ancient sorcerer pursuing immortality and evolution. He was also a man from another world, carrying knowledge that transcended this reality.
What would his domain reflect now?
"Domain Expansion," he announced, the words carrying weight that bent the air around him.
Reality shattered.
The world within a hundred-meter radius simply ceased to exist as Kenjaku's inner world manifested. In its place appeared something that made even his ancient consciousness pause in surprise.
It was a library.
An infinite library, stretching in all directions without visible end. Shelves towered toward a ceiling that might have been miles above or might have been an illusion. Books filled every shelf—millions of them, billions perhaps, each one representing some aspect of knowledge that Kenjaku had accumulated over his centuries of existence.
But the books weren't the domain's true nature.
At the center of the library stood a great machine—a combination of surgical table, printing press, and something that defied mechanical description. It pulsed with cursed energy, its purpose immediately apparent to Kenjaku's understanding.
This was where he modified things.
Within this domain, Idle Transfiguration required no contact. The machine at the center could reach anything within the library's bounds, reshaping it according to Kenjaku's will. Souls became pages to be rewritten. Bodies became books to be edited. Everything within his domain was subject to modification without resistance.
The sure-hit effect of Domain Expansion meant that no one could avoid transformation while inside his domain. His Idle Transfiguration would simply work, regardless of the target's defenses or resistance.
Kenjaku laughed.
It was a genuine laugh, carrying something that might have been joy if his emotional range hadn't been so distorted by centuries of existence. The domain was perfect—an expression of his deepest self that also served as an absolute weapon.
He called it the Library of Forbidden Wisdom.
The name felt right, resonating with something fundamental in his consciousness. This was who he was: a collector of knowledge, a modifier of existence, a being who saw reality as a text to be revised according to his preferences.
Kenjaku maintained the domain for several minutes, exploring its properties and testing its limits. The cursed energy cost was substantial but manageable with his expanded reserves. The range could potentially be extended with more development. The machine at the center responded to his thoughts instantaneously, demonstrating modification capabilities that exceeded his normal Idle Transfiguration by a significant margin.
When he finally released the domain, returning the world to its normal configuration, Kenjaku felt a satisfaction that bordered on contentment.
He had a guaranteed-hit soul modification technique now. Anyone trapped in his domain could be transformed into anything he chose, with no possibility of resistance or evasion.
Even Sukuna, with all his sealed power, would be helpless within the Library of Forbidden Wisdom.
Even Madara, when he eventually achieved his final form, would have no defense against absolute transformation.
This was a weapon that could challenge gods.
But Kenjaku knew better than to become overconfident. Domain Expansion could be countered by other Domain Expansions, the conflicting spaces canceling each other out or creating battles of domain supremacy. If an opponent's domain was stronger than his, they could potentially break through his library and impose their own will.
He needed more advantages. More techniques. More ways to ensure victory against any conceivable opponent.
Which brought him to the final item on his development agenda.
Black Flash.
The phenomenon was one of jujutsu's most mysterious effects—a spatial distortion that occurred when cursed energy was applied within a trillionth of a second of a physical impact. The result was an attack enhanced by 2.5 times its normal power, accompanied by a distinctive black spark that gave the technique its name.
Black Flash couldn't be consciously activated. That was the common understanding, at least. The timing required was too precise for human reaction time, forcing sorcerers to rely on instinct, luck, or some combination of both.
But Kenjaku wasn't limited to common understanding.
He had Idle Transfiguration, which could modify neural pathways and reaction speeds. He had Cursed Speech, which could embed commands into his own movements. He had centuries of experience and a merged consciousness that included modern scientific understanding of time and physics.
If anyone could make Black Flash reliable, it was him.
The analysis began with direct observation.
Kenjaku spent two weeks deliberately inducing combat situations where Black Flash might naturally occur, carefully noting the circumstances, mental states, and physical conditions that preceded each successful manifestation. The data was sparse—Black Flash was rare even for experienced sorcerers—but patterns eventually emerged.
The phenomenon correlated with specific mental states: intense focus combined with simultaneous relaxation, a paradoxical consciousness that was both fully engaged and completely released. It also correlated with physical conditions: perfect form, optimal energy flow, alignment between intent and action.
Most importantly, it correlated with timing—not just the trillionth-of-a-second impact requirement, but a broader temporal awareness that seemed to transcend normal perception.
Sorcerers who achieved Black Flash regularly described entering a "zone," a state where time seemed to slow and every movement felt inevitable. They weren't consciously calculating the trillionth-of-a-second timing; they were existing in a mental space where such calculations became unnecessary.
Kenjaku needed to recreate that state artificially.
The first approach was neurological. He used Idle Transfiguration to modify his brain's temporal processing, attempting to perceive time at a resolution that would allow conscious Black Flash activation.
The modification was partially successful. His perception of time did increase, allowing him to distinguish events that would have previously been indistinguishable. But the improvement wasn't enough—the trillionth-of-a-second threshold remained beyond conscious reach.
The second approach was mechanical. Kenjaku created a binding vow that would automatically apply cursed energy at the moment of impact, removing the need for conscious timing.
This approach failed entirely. Binding vows required conscious activation, which introduced delays that made precise timing impossible. The automatic application happened too late, missing the Black Flash window.
The third approach was the breakthrough.
Instead of trying to perceive or control the timing consciously, Kenjaku modified his soul to include an automatic response that operated below conscious awareness.
The modification was inspired by the reflexes that allowed the body to react to threats faster than conscious thought. The brain detected danger and initiated response before the conscious mind even registered the threat. Similar mechanisms existed for balance, proprioception, and other survival-critical functions.
Kenjaku created an artificial reflex specifically for Black Flash.
The modification worked as follows: whenever his body entered a combat state with intent to strike, a secondary processing system would activate, monitoring the approach to impact with precision that exceeded conscious capability. At the optimal moment—exactly one trillionth of a second before physical contact—this system would automatically apply cursed energy, triggering Black Flash without requiring conscious input.
The implementation required three days of continuous soul modification, each adjustment building on the previous ones until the artificial reflex was fully integrated into his spiritual structure.
Then came the testing.
Kenjaku found a suitable rock formation—large enough to demonstrate the technique's enhancement, solid enough to provide clear feedback. He approached it with combat intent, allowed his body to enter striking form, and threw a simple punch.
Black Flash.
The distinctive black spark erupted at the moment of impact, confirming that his modification had worked. The rock formation exploded, the 2.5x enhancement turning an already powerful strike into something devastating.
He tested again. Black Flash.
Again. Black Flash.
Ten consecutive strikes, ten consecutive Black Flashes. The artificial reflex was triggering with perfect reliability, transforming what had been a random phenomenon into a deliberate technique.
Kenjaku's smile widened.
He had just solved one of jujutsu's fundamental limitations. No one in history—in either history—had achieved reliable Black Flash activation. The phenomenon had always been treated as a blessing, something that happened to sorcerers rather than something they could cause.
But Kenjaku had made it controllable. Repeatable. Infinite.
Every physical attack he delivered could now be enhanced by 2.5 times.
Every punch, kick, or strike would carry Black Flash's spatial distortion.
His combat effectiveness had just increased by more than double.
The implications cascaded through his strategic planning.
Previously, he had relied on techniques and abilities to match physically superior opponents. His body, while enhanced, couldn't compete with the raw power of beings like Sukuna or the eventual jinchuriki.
But with reliable Black Flash, that calculation changed. 2.5x enhancement applied to every strike meant that his effective physical output exceeded most opponents' maximum. Combined with his speed enhancements, his predictive capabilities, his defensive techniques—
Kenjaku was becoming a complete combatant.
Strong enough to overpower most opponents directly.
Versatile enough to adapt to any situation.
Prepared enough to face threats that hadn't yet been born.
But still not satisfied.
Because somewhere in the back of his mind, the threats continued to multiply. Kaguya's Expansive Truth-Seeking Ball, which could disintegrate anything it touched. Naruto's eventual mastery of Six Paths Sage Mode. Sasuke's Planetary Devastation. Madara's Infinite Tsukuyomi.
There were always bigger dangers. Always higher peaks. Always further to climb.
And Kenjaku refused to stop climbing until he reached the absolute summit.
When he returned to Uzushio Island, Hana was waiting for him at the harbor.
Her appearance had changed during his absence—she had lost weight, developed dark circles under her eyes, and displayed the subtle tremor of someone who hadn't slept properly in days. Her expression when she saw him was naked relief so intense that it approached religious ecstasy.
"Master!" She ran toward him, abandoning all pretense of professional distance. "You're back. You're alive. I was so worried—you were gone so long—I thought—"
Kenjaku caught her before she could collide with him, holding her at arm's length with clinical detachment.
"I was training. As I told you before I left."
"But you didn't send word. Didn't let me know you were safe. I didn't know if something had happened, if Sukuna had found you, if—"
"Hana." His voice carried the authority that always silenced her. "I am capable of caring for myself. Your concern is noted but unnecessary."
She stopped speaking, but her eyes remained fixed on him with desperate intensity. The separation had clearly exacerbated her psychological condition, pushing her already-obsessive attachment into something approaching mania.
This was becoming a problem.
Kenjaku considered his options as they walked toward the Uzumaki village. He could use Idle Transfiguration to modify her psychology, adjusting her emotional responses to healthier parameters. But that risked damaging her effectiveness—her devotion, however extreme, made her a reliable subordinate.
He could use Cursed Speech to command her emotions into balance. But the effects would be temporary, requiring constant maintenance.
Or he could simply accept her current state and manage the complications as they arose.
The third option was least elegant but most practical. Hana's obsession hadn't yet interfered with her duties, and her devotion made her uniquely trustworthy for sensitive operations. As long as she remained functional, her psychological state was tolerable.
"I have new capabilities to show you," he told her, partly to distract from her emotional state and partly because the information was relevant. "My training was productive. I've developed techniques that will significantly enhance our operational effectiveness."
Hana's distress faded slightly, replaced by the eager attention she always displayed when he offered knowledge. "New techniques? What kind?"
"Several kinds. Modifications to my Cursed Speech that allow remote transformation. An enhanced version of Maximum: Uzumaki with command integration. And most significantly, a method for reliable Black Flash activation."
"Reliable...?" Hana's eyes widened. "You can use Black Flash whenever you want?"
"Essentially, yes." Kenjaku allowed himself a small expression of satisfaction. "Every physical attack I deliver now carries the enhancement. The modification is permanent and automatic."
Hana processed this information with visible awe. "That's... that's impossible. No one has ever—"
"I have. And I intend to continue achieving the impossible." He increased their pace toward the village. "Now. Report. What happened while I was away?"
Hana's report was comprehensive, as expected. The Uzumaki had continued their academic research, making modest progress on several projects that Kenjaku had suggested before his departure. Political tensions on the mainland had shifted, with several minor clan alliances forming and dissolving. Most significantly, rumors had reached the island of a new threat emerging in the northern territories—a powerful shinobi whose abilities defied conventional understanding.
"What kind of abilities?" Kenjaku asked, his interest sharpening.
"Details are vague. The reports describe techniques that manipulate time and space, allowing the user to appear and disappear without warning. Some witnesses claim he can walk through solid objects. Others say he can teleport across vast distances."
Kenjaku's mind raced through possibilities. Time-space manipulation suggested several potential identities from his meta-knowledge. The Otsutsuki had such abilities. Certain Mangekyo Sharingan techniques allowed similar effects. Hiraishin, the Flying Thunder God technique that Minato would eventually master, could explain teleportation.
But in this era, most of those abilities shouldn't exist yet.
Unless someone else had followed a similar path to his own. Unless another transmigrator or reincarnator was operating in this merged world.
The possibility was concerning but also exciting. If there was another player with meta-knowledge, they could be a threat—or an opportunity.
"Continue gathering intelligence on this individual," Kenjaku instructed. "Priority information includes their apparent age, physical description, and any observed weaknesses. If an opportunity arises for direct contact, do not engage—observe and report only."
"Understood, Master."
They reached the village, where Hiroshi was waiting with the slightly distracted expression of a scholar who had just been interrupted mid-thought.
"Shimoda-san! You've returned. Excellent. I've made a breakthrough in the theoretical integration you suggested—I believe I understand how curse technique generation relates to our sealing matrices. Your input would be invaluable."
Kenjaku allowed himself to be drawn into academic discussion, his surface attention on Hiroshi's theories while his deeper consciousness continued processing the implications of his training results.
He was stronger now than he had ever been.
Cursed Speech integrated into his core abilities.
A Domain Expansion that guaranteed transformation.
Reliable Black Flash on every physical strike.
Enhanced physical parameters, expanded cursed energy reserves, refined technique precision.
And still, the threats accumulated in his mind. Still, the challenges ahead loomed larger than any single capability could address.
Madara, with his eventual mastery of Rinnegan and the Ten-Tails.
Obito, with Kamui's perfect defense.
Kaguya, with power that transcended mortal understanding.
The Otsutsuki, with their planet-consuming ambitions.
Naruto and Sasuke, whose eventual alliance would produce the strongest team in shinobi history.
And Sukuna, sealed but not destroyed, nursing hatred that would eventually demand satisfaction.
Kenjaku needed to be ready for all of them.
Needed to exceed all of them.
Needed to become something that even gods would fear to face.
The training would continue.
The improvements would accumulate.
The villain would grow stronger.
And when the final battle eventually came—whenever it came, against whoever it came against—Kenjaku would be ready.
Because that was the only acceptable outcome.
Because that was the story he was writing.
Because he refused to be ordinary ever again.
The greatest villain of the age was becoming something more.
Something unprecedented.
Something eternal.
And the world would learn to tremble at his approach.