Muzan had been struggling lately, and Oboro knew it all too well.
Reports flooded in from every corner of Japan, there were countless witnesses to the escalating battles between the Demon Slayer Corps and the demons. These confrontations had become frighteningly frequent over the past few months and always ended the same way: the Demon Slayer Corps emerged victorious.
Their breathing techniques were finally showing their devastating effectiveness.
On this particular night, Oboro trained alone in his courtyard, his fists and feet moving with practiced precision through the air. His mind wandered to the Sun Breathing technique that Tanjuro Kamado had refined with his guidance. Oboro had only taught him how to prevent the technique from harming the user, but before leaving Mount Kumotori, he witnessed something remarkable: Tanjuro's Kagura dance had evolved once again.
It seemed the man had developed it further through his own intuition and dedication.
This revelation struck Oboro with a profound realization. Although the beings in this world had limited raw power, their wisdom and determination were not to be underestimated. Through the collective will and relentless effort of countless individuals, they could elevate any foundation to new heights.
The Kamado clan's unwavering spirit, combined with the pillars of the Demon Slayer Corps, might unlock new dimensions within breathing techniques. This development would deepen his understanding of "inner breath," the mysterious force connecting body and spirit.
All of the martial arts and cultivation methods recommended by his system stemmed from his memories of Earth. Every technique, every ounce of strength, and every skill Oboro commanded originated from that foundation and was refined through his experiences in different worlds. However, he had now reached the pinnacle of conventional martial arts, and further progress seemed impossible.
Yet, he was certain that more powerful methods of practice existed.
The breathing techniques had transcended their earthly origins as mere "martial" concepts. They touched upon the mystical, delving into self-cultivation and spiritual refinement bordering on the supernatural.
However, the system's guidance in this realm was frustratingly vague, offering no concrete path forward. Most of the information came from half-remembered fragments of movies and media he had consumed in his previous life, an "incomplete version" that the system had evolved based on its understanding of human anatomy.
Breaking through would require more than physical mastery.
The next step would involve not just the strength of flesh and blood but also the essence of the soul, something the system could never quantify or calculate.
Hunter x Hunter, across all timelines and dimensions, was a high-level world, but far from the apex. If he ever found himself in a truly powerful realm, his current strength would be woefully inadequate.
However, Tanjuro Kamado and the Demon Slayer Corps had given Oboro something precious: hope. They represented the brilliance of inherited will, a force transcending individual limitations.
Perhaps he could harness this collective determination to shatter the barriers of martial arts and achieve true enlightenment. It might take generations to bear fruit, but the combined power of breathing techniques, his methods, and the system's assistance would eventually make him stronger.
"This is the fundamental difference between inherited will and personal will," Oboro mused, finally stopping and exhaling slowly. "Personal will belongs to the individual alone, while inheritance represents the combined efforts of countless souls, the crystallization of life itself."
According to the system's projections, if breathing exercises evolved one step further, they would transcend traditional martial arts entirely. They would approach what Earth's Manhua/Manhwa enthusiasts call "immortal cultivation," the path to becoming something beyond human limitations.
The idea of achieving immortality or enlightenment remained unproven on Earth, but Oboro was certain it involved the soul. Here, in this world rich with supernatural forces, such legendary achievements might actually be possible.
If he could sublimate his soul power through these techniques, he would reach unimaginable heights in his previous existence.
Chiyoko, who had been waiting patiently nearby, approached as Oboro finished training. She draped a black haori over his shoulders with practiced care.
"Hmm?"
Suddenly, Oboro's eyebrows shot up as his senses detected something amiss. His mansion was located in a serene part of the city, surrounded by mountains, beautiful scenery, and flowing water. Even at midnight, the air was usually filled with the natural symphony of insects and night birds.
But now, an unnatural silence had descended; everything was completely quiet.
The silence was terrifying in its completeness.
"Go inside and don't come out," Oboro commanded.
Chiyoko nodded without question and hurried toward the house.
"So you've finally found me," Oboro said, his lips curving into a knowing smile.
He had long anticipated that Muzan would send demons to make contact. His existence defied Muzan's understanding of the world. He was certain the Demon King would lack the courage to appear personally.
"Such a foul stench and such an incredible presence," Oboro murmured as he picked up a wooden training sword and positioned himself to face the gate. "How fascinating."
Despite Oboro's careful manipulation of his identity through shogunate connections, it wouldn't be difficult for the Ubuyashiki clan or Muzan to discover his location. Yet, the shogunate had remained peaceful recently, with no unusual incidents.
This suggested that Muzan's influence in this era extended to the highest levels of power, possibly even among the ruling elite.
"A feudal lord, perhaps?" Oboro wondered aloud.
Daimyōs wielded considerable authority during the Edo period, functioning as regional rulers under the shogunate's oversight. Some enjoyed substantial autonomy, while others served as branch administrators. Many were required to send family members to the shogunate as hostages to ensure loyalty.
This system of controlled power bred stability and resentment in equal measure.
Whoosh.
An almost inaudible sound announced the arrival of his visitors. At the entrance of the mansion stood a warrior, silhouetted against the full moon.
He wore a purple kimono adorned with snake patterns and black spots, as well as a black hakama, and he carried a samurai sword. His hair was bound in a traditional topknot. But it was his face that commanded attention: six bloodshot eyes opened and closed across his features, creating a visage that would shatter the sanity of ordinary humans.
This was Gyokko Tsugikuni, the elder brother of Tsugikuni Yoriichi and a survivor from the Warring States period to the present day. Now known by a different name: Kokushibo.
Creak.
Oboro glanced down as the firmly closed gate of the mansion swung open. Another familiar figure stepped through, poking his head inside first. Upon spotting Oboro, his face lit up with a cheerful smile.
"Ah, there you are! I hope I'm not disturbing you." The newcomer's tone was disarmingly pleasant. "I intended to knock politely, but this gentleman moved so quickly that I had to be direct to keep up. Otherwise, when Lord Muzan's mission is completed, it will seem as if I contributed nothing at all."
Doma, Upper Rank Two.
"So early in your career?" Oboro observed, noting the kanji in Doma's eyes with interest.
It was still years before the end of the Edo period, and Gyutaro and Daki had yet to be born.
"I didn't expect such courtesy from demons," Oboro remarked with amusement. "You're not disturbing me at all. I was planning to stay up a while longer anyway."
His expression grew more serious. "Muzan didn't come himself?"
"Ah!" Doma covered his mouth in exaggerated surprise, then broke into a delighted grin. "You really do know everything, don't you? And if my senses are correct, it seems you've returned to being human."
"More or less," Oboro confirmed.
"How did you manage such a thing?"
From Doma's question, Oboro realized that Muzan had kept his demons ignorant of the blue spider lily's true purpose and had used them merely as unwitting searchers.
Doma couldn't afford to underestimate the human before him. They all knew what had happened to Upper Rank Five: Gyokko had been utterly crushed.
Even more significantly, this man had single-handedly transformed the entire Demon Slayer Corps into a formidable force.
"You must have heard of the blue spider lily. The flower Muzan has been desperately seeking?" Oboro's smile carried subtle menace.
The moment those words left his lips, both Kokushibo's and Doma's expressions shifted dramatically. They knew of Muzan's obsession with the blue spider lily, and they knew that any clues about its location would earn them rewards far beyond simple favor.
"How curious," Doma said, taking a step closer. "You already possess incredible power. Why would you choose to return to being weak and helpless? Don't you see that humans are merely empty shells, driven by base desires and lacking true purpose? I can tell you're special, so why make such a foolish decision?"
"People have different preferences and aesthetic values," Oboro replied simply.
As he studied Doma's perpetual smile, undisguised disgust crossed his features. "You remind me of someone I once despised deeply."
The memory of Pariston Hill flickered through his mind. Though their personalities differed completely, something about their auras triggered the same visceral revulsion.
"How hurtful," Doma said, her voice maintaining its gentle, almost sweet quality despite the criticism. "That makes me quite sad."
He continued his gradual approach. "Would you be willing to come with us? Lord Muzan is eager to meet you. Perhaps we could become friends. I'd rather not fight you if possible. Oh, and if you have any wishes or desires, please share them. I might be able to fulfill them."
While Doma engaged in seemingly casual conversation, Kokushibo remained motionless and silent. His purpose was clear: careful observation and analysis of their target.
Based on the intelligence he'd gathered, the man before them was no ordinary opponent. Even Gyokko had nearly died at his hands, completely outmatched and overwhelmed.
More importantly, Oboro had sensed their approach long before they arrived and had been waiting for them.
Doma's small talk created time for Kokushibo to study their target while positioning himself for potential combat.
"You're both very welcome here," Oboro said suddenly. He raised his wooden sword and ran his fingertips along its length as if it were a real blade.
His gaze fixed on Kokushibo with particular intensity. "Especially you. I'm genuinely surprised by your arrival."
"Out of courtesy, I'm going to show you something special. Something you'll definitely appreciate."
Oboro's breathing pattern shifted subtly but noticeably.
"I'm quite pleased that Muzan sent the two of you to serve as my new test subjects."
A stream of heated breath escaped from the corner of his mouth, shimmering like a flame in the moonlight.
It was Sun Breathing, the original technique that had nearly destroyed Muzan centuries ago.
"Come then," Oboro said, his voice carrying deadly anticipation. "Let's have some fun. Don't let this beautiful night go to waste."