Gyutaro possessed his own distinct fighting style, honed through years of brutal survival in the Entertainment District.
Oboro had no intention of teaching him offensive combat techniques; those would only dilute the demon's natural ferocity. Instead, Oboro focused on refining Gyutaro's body movements and footwork, adding subtle techniques that complemented his existing arsenal without compromising his raw edge.
This foundation mattered most to Gyutaro's development.
He could only accumulate practical experience through continuous battle, the clash of blade against claw, and the dance between life and death.
Throughout this intensive training period, Gyutaro and Daki remained secluded within Oboro's mansion, avoiding the outside world entirely. The tension in the air was palpable; several Hashira had taken up positions throughout the city, their watchful eyes never straying far from the estate. Their presence lingered like storm clouds, heavy with unspoken threats.
Yet, they made no move to attack.
Oboro had initially anticipated that these three Hashira would eventually attack. After all, exterminating demons was their sacred duty, ingrained in their souls through generations of tradition and loss.
But, to his genuine surprise, the trio seemed to abandon their vigil entirely, melting away into the shadows as mysteriously as they had arrived.
This development caught him completely off guard.
The Demon Slayer Corps was renowned for its unwavering resolve; its members' will burned pure and bright, and they never retreated in the face of evil. Such a tactical withdrawal was highly unusual, almost unprecedented in their history.
"It seems the current leader of the Demon Slayer Corps possesses more strategic depth than his predecessors," Oboro mused, stroking his chin thoughtfully. The implications were intriguing.
Under Oboro's guidance, Gyutaro's close-combat abilities improved at an extraordinary pace. His natural talent for violence, when properly channeled and refined, revealed itself to be exceptional. In the world of Nen users, such raw potential would have marked him as a prodigy, someone destined to become an exceptional combatant.
However, there remained a noticeable gap between Gyutaro and the true monsters Oboro had encountered in his travels.
The disparity wasn't physical; Gyutaro's body was already a devastatingly efficient weapon. The difference lay in the realm of the mind, in the subtle complexities of tactical thinking and adaptive strategy.
For a year, Oboro served as Gyutaro's protector and provider, ensuring the demon received adequate "nourishment" to maintain his strength. During this time, they sparred almost nightly, with each bout designed to push Gyutaro beyond his current limitations.
Meanwhile, Daki received considerably less direct attention. Oboro would occasionally offer her guidance, helping her refine her use of the Blood Demon Arts in combat scenarios. However, his focus remained primarily on her brother.
The siblings' combined strength hinged entirely on Gyutaro's development, not Daki's flashier abilities.
Eventually, the time came for Gyutaro and Daki to leave. They had received their final assignment from Oboro: a singular training mission that would determine their ultimate fate.
Success would mark their graduation, granting them complete freedom to pursue their desires without restraint. This autonomy was the price Oboro demanded in exchange for the power he had bestowed upon them.
The mission was brutally simple: hunt down and devour all the Upper Ranks serving under Muzan.
This task was essential for Gyutaro's continued evolution. Cannibalism among demons provides exponential strength gains, triggering rapid evolution of flesh and blood, an opportunity that both the inheritors and Muzan's forces understand implicitly.
Without this accelerated growth method, gradual development would take far too long to be practical.
Their success depended entirely on Gyutaro's capabilities and determination.
Oboro's gift of the black haori and selection of Gyutaro as a special candidate spoke volumes about the demon's potential. However, potential means nothing without the will to realize it.
Daki, however, harbored different ambitions. She yearned to become an oiran and be celebrated for her beauty, becoming renowned throughout the land. The violent path that Oboro had laid out for them held no appeal for her refined sensibilities.
Fear of Oboro's power kept her from voicing her objections, but her resentment simmered beneath the surface.
She believed that once Gyutaro eliminated the Upper Ranks, they would break free from their current master's control and achieve independence.
This fundamental disagreement created tension between the siblings. Gyutaro showed genuine respect and gratitude toward Oboro, an attitude that only served to deepen Daki's frustration and isolation.
"Have I really accumulated this much?"
One quiet evening, Oboro accessed his system's inventory and chuckled softly at what he saw.
Every available slot bristled with cards of various types and qualities. The collection represented months of careful cultivation and strategic harvesting.
Some cards had already expired, their power fading with time.
These expired items consisted primarily of flesh and blood samples from ordinary demons, creatures too weak to provide lasting value.
The most valuable specimen was the silver-level bloodline card from the evolved inheritor Yasuhara.
Close behind were the various Blood Demon Art skill cards he had collected, each representing a unique supernatural ability.
A substantial collection of Nichirin blades completed his arsenal of weapons.
The Swordsmith Village had maintained its relationship with the Demon Slayer Corps for countless generations, operating beyond the shogunate's direct interference. These specialized weapons, forged with rare materials and imbued with demon-slaying properties, far exceeded ordinary steel in quality and effectiveness. They were among the few valuable resources available for plundering in the Demon Slayer world.
Oboro's subtle influence had orchestrated the endless wars and turbulent political climate of recent decades.
Chaos bred opportunity, and death provided him with ample chances to "collect dividends" from the resulting conflicts.
He hadn't simply remained idle during his time in this world.
The relationships he fostered between the shogunate and the Demon Slayer Corps served a dual purpose: they facilitated his resource gathering while maintaining the appearance of legitimate cooperation.
"But what surprised me most was the appearance of this particular card."
His attention focused on a single, extraordinary item.
This special card had only manifested a few days ago.
This enhancement occurred after Oboro absorbed the Will of Inheritance, amplifying his soul and expanding the system's functional range.
Experience Card.
Creating this type of card required extracting the target's soul essence, a process that inflicted irreversible damage on the source.
This particular specimen ranked as black iron level, indicating the conversion target's relatively modest strength. However, its effects were remarkable. The card could instantly grant the user extensive combat experience, effectively transforming an ordinary person into a "master" with rich battlefield knowledge.
While it provided no direct power increase, experience is an invaluable commodity.
Oboro's current inventory included potentially corrupting bloodline cards, Nichirin Blade weapon cards, Blood Demon Art skill cards, and now, experience cards.
These resources could enable him to create formidable warriors out of thin air.
Despite their impressive quantity, the cards' quality was relatively modest. Oboro planned to continue his "Inheritor" strategy in this world, investing most of these lower-tier resources in personnel from the three major factions to force rapid advancement.
He would nurture and cultivate them like prize specimens.
He would use inferior cards to strengthen his subjects and then harvest superior cards from their enhanced forms.
Based on his analysis of the Demon Slayer world's power ceiling, the highest-quality cards available would likely only reach the gold tier. This assessment was supported by the fact that Yasuhara's flesh yielded only silver-level materials.
Muzan and the complete Sun Breathing technique should be the only gold-tier resources available.
As power systems evolved and strengthened, all associated resources would upgrade accordingly. This meant that he might eventually obtain platinum-level cards through continued cultivation.
This approach would save considerable time and accelerate his departure from the Demon Slayer world.
Oboro had a growing intuition that his next destination would be far more challenging. The progression of Hunter x Hunter suggested that his initial world had been deliberately chosen as the weakest possible starting point, one of the lower-tier realms. Logically, subsequent worlds would only increase in difficulty and danger.
The nature of future challenges was completely unknown.
Therefore, he needed substantial resources to hedge against potential threats. Even if he encountered serious danger in the next world, he would have enough trump cards to survive.
His current situation wouldn't allow him to maintain the same comfortable distance he had in Demon Slayer, where he could manipulate events from behind the scenes without direct involvement.
Additionally, being in a lower-tier world allowed Oboro to perceive the will of the "Demon Slayer World" and sense the existence of the metaphysical "small tree" that governed it.
This revelation indicated that each world possessed its own unique consciousness and governing intelligence.
The small tree ruling the Demon Slayer realm was remarkably weak, which explained its willingness to negotiate with Oboro. Oboro's power could potentially destroy the world in various ways, posing a genuine threat to the small tree's existence.
Faced with such overwhelming force, the world's will had little choice but to compromise.
However, higher-tier worlds would present entirely different circumstances.
Beyond the question of whether Oboro could perceive a more powerful world's will, the worst-case scenario was attracting hostile attention from a superior governing intelligence.
During his time in Hunter x Hunter, not even at the peak of his power, he had never sensed the ideological framework or governing consciousness of a higher-tier world.
When he originally entered Hunter x Hunter as an ordinary Earth soul, his weakness as an interdimensional stowaway allowed him to slip beneath the world's notice entirely.
But circumstances had changed dramatically.
His arrival in Demon Slayer immediately triggered contact with the local governing intelligence, demonstrating his increased profile and power.
Not every world would extend such cooperation and accommodation.
The small tree's submissive attitude resulted directly from the power imbalance between them.
While a world's will might not be able to eliminate the weaker party directly, it could certainly manipulate fate and circumstances. For example, it could arrange for him to encounter Muzan under hostile conditions or engineer situations in which his actions would provoke powerful enemies.
Such guided misfortune could easily prove fatal.
This possibility is precisely why Oboro chose not to leave the Demon Slayers immediately after achieving his initial objectives. To him, the world was a crucial refueling station.
Although Demon Slayer's power system operated at a relatively low level, it still contained valuable resources.
Preparation was paramount, and he intended to depart only when he was fully equipped for whatever lay in wait for him in the darkness between worlds.