Urokodaki Sakonji was genuinely shaken when he learned that Ren Kuroda had actually succeeded in creating his own breathing technique.
He knew better than anyone that not every swordsman was suited to Water Breathing. A breathing style had to align with a person's temperament, instincts, and innate talent. When Ren had calmly stated that Water Breathing didn't suit him and that he intended to develop something of his own, Urokodaki had merely smiled at the time.
If breathing techniques were that easy to create, there wouldn't have been so many styles passed down through centuries of blood and sacrifice.
And yet—six months later—Ren had done the impossible.
Although this so-called Demon Breathing currently consisted only of the breathing method itself, without any accompanying forms or techniques, Urokodaki understood something crucial:the breathing method was the core of everything.
Once a breathing style existed, techniques would naturally follow.
If Urokodaki Sakonji felt shock, then Tanjiro felt nothing but awe.
Over the same six-month period, Tanjiro had focused entirely on tempering his body—strength, endurance, reflexes—just barely reaching a level that satisfied Urokodaki.Meanwhile, Ren had quietly crossed an entirely different threshold.
He had created his own breathing technique.
After succeeding, Ren bid farewell to both Urokodaki Sakonji and Tanjiro.
He had learned nearly everything he needed. Now that he had even mastered the mysterious concept of breathing techniques, there was no longer any reason for him to remain.
Between the time he had already spent wandering this world and the six months devoted to developing Demon Breathing, his remaining time was dangerously limited.
The system had never explained what would happen if he failed his mission—but Ren had a strong feeling that failure meant being trapped in this world forever.
That alone was reason enough to accelerate his progress.
Of the two years granted by the system, nearly one had already passed.And in that time, Ren had slain only fifty-six demons—still far from the required total of one hundred.
The Twelve Demon Moons were another looming problem.Beings of that level weren't just terrifyingly powerful—they were also incredibly rare. Encountering one in a world this vast depended almost entirely on luck.
In short, wandering aimlessly in search of rampaging demons was far too inefficient.
Worse still, without a Nichirin Blade, his killing efficiency was abysmal.
That was why, after receiving Urokodaki Sakonji's letter, Ren set off for Mount Fujikasane.
Every year, the Demon Slayer Corps held a final selection exam.Those who passed would officially join the Corps—and receive their own Nichirin Blade.
Ren had never planned to join the Demon Slayer Corps.But reality left him little choice.
They possessed the equipment, intelligence networks, and infrastructure he desperately needed.
According to Urokodaki, the letter explained Ren's unusual circumstances to his lord. Whether Ren would stay with the Corps or leave afterward would be entirely his own decision.
The fact that Urokodaki Sakonji was willing to write such a letter at all spoke volumes.
Ren's talent had impressed him deeply—so deeply that he was willing to stake his own reputation on the boy.
After observing breathing techniques for only a month, Ren had created his own style in half a year. Even before mastering it, he already possessed power on par with a Pillar.
Coupled with the physical strength and terrifying regeneration inherent to demons, Urokodaki was certain of one thing:
The moment Ren joined the Demon Slayer Corps, he would instantly rank among its strongest members.
Since the death of Yoriichi Tsugikuni, the founder of breathing techniques, humanity had steadily fallen behind the demons.
Though the Pillars were regarded as the pinnacle of human strength, even they were merely comparable to the Twelve Demon Moons.As for killing Muzan Kibutsuji—
That bordered on the impossible.
No—history made it clear.
Across countless generations of Pillars, none had even stood a real chance against the Upper Moons, let alone Muzan himself.
The Twelve Demon Moons were divided into Upper Six and Lower Six.Though they shared the same title, the gulf between them was immeasurable.
Over the past century, the Lower Moons had been repeatedly wiped out and replaced.The Upper Moons, however, had remained unchanged for one hundred and thirteen years.
Even the weakest among them—Upper Moon Six—had personally killed seven Pillars.
Such was the overwhelming disparity between humans and demons.
If Yoriichi Tsugikuni hadn't once nearly slain Muzan, forcing the Demon King into years of recovery, the Demon Slayer Corps might not even exist today.
But Yoriichi had been dead for generations.
And with the only being Muzan ever feared gone, demons had grown increasingly bold in recent years.
A swordsman like Yoriichi—someone seemingly born to wield a blade—was extraordinarily rare.
Urokodaki had always believed that a second such existence would never appear.
And then—
Ren Kuroda arrived.
He didn't yet possess Yoriichi's overwhelming power.But in Ren, Urokodaki saw the same terrifying talent, the same depth of comprehension, the same instinctive understanding of the sword.
Perhaps Ren wasn't purely human.
But opportunities like this couldn't be discarded because of identity alone.
No one knew Muzan Kibutsuji's true strength.Everyone who had ever faced him—aside from Yoriichi—was dead.
Against such a demon king, humans were hopelessly inferior, both in raw power and in recovery.
Even the current nine Pillars—stronger than any generation before them—still stood little chance.
And yet…
Urokodaki Sakonji saw hope in Ren.
That was why he used the weight of his years, his name, and his reputation to write that letter—recommending Ren Kuroda for entry into the Demon Slayer Corps.
The future remained uncertain.
But to Urokodaki, sacrificing a bit of his insignificant pride in exchange for the possibility of a powerful future demon slayer was more than worth it.
Even if things didn't unfold as hoped, his year spent observing Ren had revealed something else:
Ren held no hatred for humanity.
Even if he didn't ultimately remain with the Demon Slayer Corps, he would never become an enemy of mankind.
Having lived as long as he had, Urokodaki Sakonji trusted his judgment.
He believed—deeply—that he was not mistaken about Ren Kuroda.