The training method bore striking similarities to the martial arts traditions of his original world-techniques that required patient dedication and years of meticulous practice to master. The complexity was staggering, requiring the same level of dedication he'd invested when he first learned Nen in the Hunter x Hunter reality.
Every aspect of this power required careful study. From the basic circulation patterns that guided energy through his meridians to the advanced techniques that could store concentrated qi in specific acupuncture points, mastering these abilities would require months or even years of intensive training.
Fortunately, his enhanced soul provided a significant advantage. Where an ordinary practitioner might take decades to achieve basic competency, Oboro's extraordinary spiritual strength would double, perhaps triple, his cultivation speed. However, even with these advantages, the road ahead was still a long one.
He had settled into a rigorous training routine, using his transformed demonic body as a foundation for qi development. Each morning began with basic breathing exercises designed to awaken dormant energy channels. Afternoons were devoted to circulation exercises, guiding qi through increasingly complex patterns until the movements became as natural as breathing itself.
The peaceful rhythm of this cultivation was exactly what he needed to prepare for the challenges of the next dimension. Here in his modest home, surrounded by the familiar sounds of daily life in the mountain town, he was able to focus on his inner development without external distractions.
This tranquil existence came to an abrupt end when an uninvited guest appeared in his bedroom without so much as a knock.
"My lord... it is time."
Doma's voice carried his characteristic musical quality, though something darker lurked beneath the pleasant tones. The ice demon stood just inside the doorway, his rainbow eyes reflecting the moonlight streaming through the window. Despite the casual smile that played across his features, his presence exuded barely contained anticipation.
The meaning of his words was unmistakable. After years of preparation, maneuvering, and calculated strikes against Muzan's power base, the final confrontation was at hand.
"Over the years, Muzan has been unable to eliminate you, yet you've managed to expand the Cult of Eternal Paradise to remarkable proportions," Oboro observed, not bothering to rise from his cross-legged meditation posture. "You have done an excellent job."
Doma's transformation was immediately apparent to anyone with spiritual perception. Where once his soul had been a chaotic jumble of ingested fragments, it now displayed a sophisticated organization and purpose. The countless souls he'd absorbed - both human and demonic - had been arranged like pieces on a vast chessboard within his consciousness.
These remnant spirits were no longer writhing in confused agony. Instead, they knelt in perfect formation around Doma's core essence, their remaining thoughts focused entirely on worship and adoration. It was a grotesque mirror of his earthly cult, where living worshippers offered the same absolute devotion.
Most remarkably, Doma had learned to command these soul fragments directly. They weren't just passive trophies anymore, but active spiritual assets that could be used at his will. The level of mind manipulation required for such control indicated that his understanding had advanced far beyond basic techniques.
"While Master Muzan possesses tremendous power, his personality remains... predictable," Doma replied with a gentle laugh, pressing a finger to the corner of his mouth in his characteristic gesture. "After serving under him for so many decades, I have learned to read his moods and anticipate his reactions. Predicting what he wants to do - or what he will do - has become almost trivial."
His smile widened in genuine amusement. "Though perhaps I should not claim credit for cleverness. The truth is that Master Muzan was never very good at hiding his emotions. He probably never considered Kokushibo and I a threat significant enough to warrant serious deception.
"Contempt would be a more accurate description," Doma continued thoughtfully. "He truly looks down on us."
Despite all that had transpired between them-the betrayal, the conflicts, the open rebellion-Doma still referred to Muzan with the respectful title of "Master. Whether this represented genuine lingering loyalty or calculated psychological manipulation remained unclear.
"In recent years, after he realized he couldn't simply eliminate us by brute force, he has rarely appeared in public," Doma continued his analysis. "I suspect he's devoted most of his time to studying soul power techniques. As one would expect from Master Muzan - even in the face of overwhelming opposition, he focuses on fundamental improvement rather than desperate tactical measures."
The ice demon's expression grew more serious as he considered the implications. "Finding his current location required considerable effort on my part. He has become remarkably adept at hiding when he chooses to do so."
"When and where?" Oboro asked, cutting through the long explanation with his typical directness.
"Ten days from now, in Ueno," Doma replied without hesitation.
"Understood."
Oboro nodded once and began to calculate the logistics. Before leaving the Demon Slayer world for good, this final battle demanded his personal attention. Aside from the obvious need to gather resources and turn certain abilities into portable experience cards, witnessing this confrontation would provide crucial insight into how his inherited will had influenced the world's development.
Muzan was well aware of his situation. The Castle of Infinity no longer offered any real protection - not if Oboro had the ability to break through dimensional barriers at will. As the architect of so many fates, Oboro wouldn't just let the demon king escape when the time came.
Running was pointless. Victory through combat was the only way for Muzan to survive.
As the progenitor of all demons, he retained certain fundamental advantages over his rebellious subordinates, regardless of their mastery of Soul Force techniques. However, Doma wasn't foolish enough to believe that he and Kokushibo could defeat Muzan by direct confrontation alone.
That's why he would make sure that the battlefield would be as chaotic as possible. The more factions involved, the better his chances of emerging victorious from the melee.
Both sides were playing to Oboro's carefully orchestrated plan. He had deliberately chosen not to kill Muzan in that earlier encounter at the Castle of Infinity, allowing events to reach this inevitable climax.
Doma had recognized this deeper strategy from the beginning. His ability to locate Oboro's residence and approach him without invitation proved that certain unspoken agreements existed between them.
"Is there something else?" Oboro inquired when Doma made no move to leave.
"If I emerge victorious in the end... would you consider granting a personal request?" The ice demon's eyes sparkled with an emotion that seemed almost vulnerable - a stark contrast to his usual calculated charm.
"What kind of request?"
"Let me be your sole successor."
A faint flush colored Doma's pale cheeks as he spoke, lending an unexpected humanity to his typically perfect features.
The word 'successor' carried different connotations than 'heir'. While heirs simply received power or knowledge, successors were chosen to carry on a legacy-to become an extension of their master's will and purpose.
The emphasis on "merely" revealed even darker ambitions. Once Muzan was eliminated, Doma intended to systematically destroy every other individual who had received gifts from Oboro. He wanted exclusive access to the power and wisdom that came from serving as Oboro's chosen representative.
This desire stemmed from something deeper than mere ambition. Unlike his complicated relationship with Muzan-which had been built on fear, respect, and eventual rebellion-Doma saw Oboro as the embodiment of perfection itself. In his eyes, Oboro represented divine artistry made manifest, a work of cosmic beauty worthy of absolute devotion.
Over the years, Doma had discovered that the spiritual ecstasy provided by soul power far exceeded any pleasure he'd derived from Muzan's blood. The difference was not merely quantitative, but qualitative - like comparing the flickering of a candle to the blazing radiance of the sun itself.
"Focus on survival first," Oboro replied with studied neutrality, his tone betraying nothing of his thoughts on the request.
Doma's smile never wavered, though his eyes betrayed a flicker of disappointment at the noncommittal response. After a formal bow that somehow managed to convey both respect and barely suppressed desire, he turned and disappeared back into the shadows beyond the window.
The coming war would determine not only the immediate fate of the major players, but the fundamental direction this world would take for centuries to come. On a more personal note, it marked the end of Oboro's journey through his second dimensional reality.
Compared to the personal will he'd cultivated during his time in Hunter x Hunter, the inherited will he'd practiced in the Demon Slayer world felt somehow inadequate. Perhaps his past experiences had affected his perception, making it impossible to fully embrace this new form of supreme will.
The problem lay in the nature of the inherited will itself. To truly embody such power, one had to first be moved by the 'brilliance' of the inherited legacy - to be infected and transformed by its essential spirit before attempting to carry it forward.
But when Oboro first arrived in this world, he'd had no real understanding of what Inherited Will actually meant. It was only through encounters with figures like Rengoku Tenjuro, the Ubuyashiki Clan, his own heirs, and the remarkable achievements of the Demon Slayer Corps and the Kamado Clan that he had begun to grasp its significance.
These experiences had indeed had a psychological impact and caused genuine wonder. They had provided insights that had elevated his soul and expanded his consciousness in meaningful ways.
But he'd discovered that inherited will is inextricably linked to destiny, background, and formative experiences. It required an authentic connection to the inherited legacy. As a dimensional traveler with no real roots in this reality, his position as either carrier or originator of such a will remained fundamentally weak.
If the Demon Slayer world had been his first destination - if he'd started out as an ordinary human and participated naturally in the unfolding plot - he might have been able to integrate more successfully. Joining the Demon Slayer Corps as a regular member, rising through the ranks to become a Hashira, experiencing the full emotional journey that such a path required...
But because this was a lower-level world, his existing strength had left little room for meaningful growth or real challenge. He could not experience the gradual evolution that would have allowed for true assimilation into the essential spirit of this reality.
His time in Hunter x Hunter had left permanent marks on his soul that couldn't be erased or ignored.
That was why he'd always referred to the Demon Hunter world as a "halfway gas station" rather than a true destination.
There was another crucial factor to consider. While practicing the inherited will had been important during his stay here, it hadn't been his only goal. Gathering resources, developing his various abilities, and preparing for future challenges had demanded equal attention. He couldn't afford to fully dedicate himself to the Inherited Will at the expense of these other vital concerns.
If he were forced to evaluate his execution of the Supreme Will during this world journey - system evaluations aside - Oboro would have to admit failure.
Still, the experience had not been entirely without value. His soul had undergone a subtle but meaningful transformation, and he now truly understood the profound weight that the concept of 'inheritance' itself carried.
The system's capabilities had been enhanced, and several new functions had been added to its repertoire. With proper application in future worlds, these enhancements could lead to a true evolution of the system's core capabilities.
"The tragedy is that here in the Demon Slayer world, I've witnessed the rich tapestry of human emotion and connection," Oboro muttered to himself with bitter irony. "It's a completely different spectrum of experience than Hunter x Hunter - something I'd always overlooked or dismissed. But what I've done here, from certain perspectives, is undeniably tainted with sin."
He laughed softly at his own self-reflection, though there was little real humor in the sound.
There had been no alternative. Without the actions he'd taken - the manipulations, the calculated interventions, the deliberate cultivation of conflict - establishing himself in the next world would have been virtually impossible.
His ultimate goal remained unchanged: to return to Hunter x Hunter with the power to explore its deepest secrets.
He finally understood what the ancient tree deity of the Dark Continent had tried to communicate during their brief encounter.
Supreme will, whether personal or inherited, when developed to its absolute limits, connected with something far more fundamental and mysterious than mere power or technique.
This connection led to miracles.
Will possessed the ability to create true miracles - phenomena that transcended normal causality and defied conventional understanding.
Miracles were the ultimate form of reality manipulation, far beyond the influence of rules, souls, or any other force he'd encountered.
The Tree God had tried to warn him that in the deepest reaches of the Dark Continent, will-based miracles were not only possible, but commonplace. There were beings whose mastery of the highest will allowed them to reshape existence itself according to their wishes.
That was the level of power Oboro would need to truly explore those forbidden depths and uncover their secrets.
Everything he'd done - every sacrifice he'd made, every manipulation he'd orchestrated, every bond he'd formed and broken - had been in the service of reaching that transcendent state.
The upcoming battle in Ueno would be the final test of whether his efforts in this world had brought him closer to that ultimate goal.