Jigoro Kuwajima was Zenitsu's master.
Sakonji Urokodaki, meanwhile, trained many figures—including Tanjiro Kamado, Giyu Tomioka, Sabito, and Makomo.
Kanjiro Kamado had also already been born.
On Muzan's side, there were a few Lower Moons that Oboro recognized by name, such as Ubume and Kai.
Sadly, the timeline for these two demons had strayed completely from the original story. No sooner had they begun to show their strength than they were slain.
Muzan had far too many enemies.
Shifts in the world were so drastic that even the Taisho-era government had published an official journal, continuously recording and updating intelligence on every faction and situation.
Its purpose was to help the public guard themselves against demons.
In this version of the Demon Slayer world, nothing remained hidden.
Everyone knew Muzan was the progenitor of all demons.
Then there were the Successors—demons guided by the deity Miketake no Kami, who claimed their mission was to "remake humanity and change the world."
They were essentially demon cultists.
In their eyes, the world as it stood was already "broken."
Unlike the demons under Muzan's command, they followed a warped ideology.
The "Miketake no Kami" they spoke of was none other than Oboro himself.
Humanity, however, refused to believe such claims.
In human lore, Miketake no Kami—the god Oboro represented—was a divine being symbolizing strength.
A bringer of hope.
A benevolent deity overflowing with positive power.
The figure revered by the Successors was nothing like the god humans knew.
Even the long-secret Demon Slayer Corps had been brought into the light.
This ancient order of demon hunters had existed since time immemorial.
Across the country, strongholds of all sizes had been built, gathering scattered populations into secure settlements and preventing civilians from being turned into demons.
Hardly anyone still lived deep in the wilderness; traditional hunters, for example, had become a rare sight.
Oboro's own small town was a perfect example—though sparsely populated, it was now ringed by high, protective walls.
All of this had changed in just a few short years.
To sum it up: while the world still retained its original foundation, its society, balance of power, and even its system of strength had diverged entirely from canon, now following a new path of its own.
The will of the world itself—the tiny sacred tree—had finally borne fruit, though still green and unripe.
Oboro could feel it: his time here was drawing to a close.
He would not remain until the story even began…
Of the several "seeds" he had planted, some had sprouted successfully, while others proved useless.
First seed: Soul Power
It had pushed all demons to evolve collectively to a higher level, yet yielded no true breakthroughs.
Soul Power had given rise to abilities and cultivation methods even Oboro had never researched or imagined.
In the end, this project could only be marked for resource recovery.
Whether Muzan lived or died, his Blood Demon Arts, techniques, and demonic lineage would be sealed into cards—cards Oboro would take with him to his next world.
As a harvest, this seed was technically a failure. But in elevating the Demon Slayer world's overall power system, its contribution was immeasurable.
Second seed: Gyutaro
Like Muzan, he offered some benefit to the world's collective growth.
Yet in this world, true transcendence in martial skill remained impossible.
Even after countless warriors studied Gyutaro, analyzing his footwork, stance, and combat techniques, the result was mere imitation and basic learning—never true mastery.
There was simply no way to reach a higher realm.
Pure martial arts had always been shallow in this setting.
Apart from the deceased Upper Moon Doma, scarcely anyone else was worth naming.
The world had its own ninja clans, skilled in lethal combat, yet their skill paled in comparison to that of the Zoldyck Family.
With hidden truths laid bare and every key figure exposed to public scrutiny, the actions of both humans and demons were now closely monitored.
Gyutaro's existence, at the very least, had broadened the world's understanding of martial arts—even if it remained a niche discipline.
Third seed: Breath & Circulation
This one had truly succeeded.
Kanjiro Kamado, now in his sixties, had mastered the Aura Conduit—a state similar in concept to "opening the Eight Extraordinary Meridians," yet fundamentally different.
By using his breathing technique, Kanjiro could channel inner energy into specific acupoints, storing it there until releasing it in bursts of superhuman power.
He had developed this entirely on his own, without any interference from Oboro.
Meanwhile, the Demon Slayer Corps had derived a parallel method: the Aura Vortex.
Though it shared the same core principle, it had its own unique traits. Practitioners compressed Aura endlessly within the muscles and blood of each body part, forming a tiny internal cycle—essentially installing invisible engines in every limb. As long as their Aura held out, their strength multiplied dramatically.
Aura Conduit expands outward; Aura Vortex condenses inward.
Kanjiro's technique linked all acupoints into flowing channels, allowing him to unleash stored energy in one explosive surge with zero internal resistance.
The Corps' method, however, retained Aura within localized zones. Its circulation was limited in range and scale, with no long-term storage—requiring constant breathing practice just to maintain each vortex.
Oboro's system immediately began simulating and analyzing these two forms of energy the moment it observed them.
After long calculations and drawing from Oboro's memories of Earth, it synthesized an evolved version of Breath & Circulation—one that went far beyond traditional martial arts.
It had finally become a true system of cultivation: The Dantian Aura Sea.
A method of harnessing energy rooted in Earth's ancient traditions, yet transcending them.
Breathing had become Aura Refinement.
Oboro was pleased, though not ecstatic.
Any technique classified as a "Dharma Art" inherently surpassed the power systems found in most higher realms.
Yet it still could not guarantee absolute safety in his next destination.
Oboro had never expected to develop such advanced cultivation in what was considered a low-level world like this.
Both the Kamado bloodline and the Demon Slayer Corps lived and breathed the principle of inheritance.
Oboro had only tried the experiment on a whim, yet it had worked perfectly. The resilience of this legacy truly impressed him.
The Corps would never have delved so deeply into energy cultivation without their mission to slay demons.
Kanjiro would never have achieved such heights without his drive to preserve the Sun Breathing technique.
"If I can master this Dantian Aura Sea… even in higher worlds, I could rise to the level of an Earthly Immortal," Oboro thought to himself.
Even he had only ever sensed and manipulated Aura before; the concept of a Dantian was almost mystical, something he once thought out of reach.
Now, the system provided a complete training blueprint.
"I couldn't achieve this even in my last world—Hunter × Hunter… but here, in Demon Slayer, it finally happened. Incredible…"
"Still… my worries go beyond just the power system and environment of the next world. I fear its Will above all. If it marks me as an intruder and tries to erase me before I can grow… even with the path to immortality, I could die before I ever truly begin."
Oboro understood his situation perfectly.
The Will of the Demon Slayer world could not expel him, so it had settled for cooperation—a calculated gamble.
As a traveler between worlds, he fell outside every natural fate line. To any realm, he was an anomaly.
His arrival inevitably shifted its course—like a virus altering a host.
That was why he did not celebrate too wildly, even after gaining such a powerful art.
In the end, the soul remained his greatest strength.
Every time he crossed into a new world, he would rely first and foremost on his soul and his system.
Only after securing his footing with those two foundations could he solidify everything else.
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