Afternoon.
Asuka sat cross-legged on the tatami mats of the Rengoku family dojo, Nugata resting casually across his knees.
Opposite him sat Kyojuro Rengoku, spine straight as a pine tree, eyes closed as he breathed steadily in unison.
"Exhale—" Asuka let out a long, scorching breath, a warm current flowing through his entire body.
Hearing it, Kyojuro nodded in satisfaction. "Excellent! Asuka, your Flame Breathing is becoming more and more refined. It is hard to believe only a few days have passed!"
"Feel the heat in your chest, like fuel pumping through your blood! The core lies in explosive will!"
Following his guidance, Asuka settled his mind and continued sensing the airflow within his body.
These past few days, he had been staying at the Rengoku residence, and his progress in Flame Breathing had been far faster than he had imagined.
Though more often than not, he would subconsciously circulate Wind Breathing instead, causing the two different rhythms of breath to clash within his lungs and nearly suffocate him.
But repetition had carved the pain into memory, slowly teaching him how to correct the habit.
Especially after he realized that wind was a formless, unbound blade—free and razor-sharp—while flame was a blazing sword that pursued eruption and ultimate force.
Though vastly different, the two carried faint similarities.
"Though their points of force and circulation nodes differ, their sense of rhythm feels alike," Asuka said calmly.
"Precisely so!" Kyojuro responded in his booming voice. "Asuka! Your perception is truly sharp!"
"Master once told me that all Breathing Styles trace their origin back to the original Breathing of the Warring States era. It is only natural that they share common ground!"
At this, Asuka opened his eyes and asked curiously, "Then why do we not simply learn the original Breathing directly?"
Kyojuro opened his eyes as well. His golden-red pupils held a trace of confusion. "It cannot be learned! That Breathing Style has been lost!"
Lost? Asuka's brows knit slightly as Kyojuro continued.
"The exact circumstances are unclear to me. What I know comes only from fragments spoken by Master."
"Legend says that in a distant past, the Demon Slayer Corps once faced a catastrophe that nearly wiped them out entirely!"
"In that unimaginable, brutal battle, every swordsman who had mastered the original Breathing perished. With them, the lineage was completely severed!"
He touched the Flame Breathing manual beside him. "What we inherit now are merely embers born after that calamity... but I believe that even so, we can still slay Demons!"
"As the saying goes, those who pursue the path to its end will arrive at the same destination! Whether Flame Breathing or any other Breathing Style, all are weapons to kill Demons!"
Asuka fell silent, a faint regret stirring within him that he could not glimpse the most primordial form of Breathing.
He rose to his feet, inclined his head slightly toward Kyojuro, and turned to head toward the restroom outside the dojo.
On this point, the traditional samurai-style construction of the Rengoku household proved somewhat inconvenient.
At the Butterfly Mansion, Asuka had used a Western-style toilet for the first time. Though awkward, it had been rather convenient.
Earlier, back in Hayama, he had simply relieved himself outdoors without a second thought.
Yet the Rengoku household used a shared latrine, requiring one to step outside and turn right a few paces—or else make use of a chamber pot indoors.
Not wishing to trouble the Rengoku family, Asuka chose to take care of it outside.
The afternoon sunlight carried a faint chill as it filtered through the corridor.
The air was filled with the crisp scent of grass and wood, mingled with the subtle aroma of aged timber.
Asuka had just rounded a quiet corner of the corridor when his steps halted.
The towering figure of Rengoku Shinjuro sat not far ahead, blocking the path beneath the eaves.
The flame-patterned haori that symbolized his former identity as Flame Hashira hung wrinkled over his shoulders. Several empty sake flasks lay scattered at his feet. It seemed he had barely woken before beginning to drink again.
Over these past few days, Asuka had sensed through spiritual pressure that Shinjuro had been secretly observing their training.
He never approached Asuka and Kyojuro. Sometimes he leaned against a distant wall, drinking while watching. Other times he simply dozed along the corridor, listening to the rhythm of their breathing.
What his intentions were, Asuka did not know.
Just as Asuka prepared to silently walk around him, Shinjuro suddenly swung his arm without warning.
Thud!
A tattered book with a red cover was hurled roughly at Asuka's feet.
"Take it." Shinjuro's voice was hoarse, every word steeped in liquor. "If you insist on wasting your time learning useless things, then see clearly for yourselves."
"See clearly... just how useless these so-called Breathing Styles truly are."
Asuka bent down and picked up the battered volume—The Book of the Twenty-First Flame Hashira.
Without another word, Shinjuro tipped his head back and drained a long gulp of sake. His throat bobbed violently before he rose unsteadily and staggered off into the shadows of the corridor.
When Asuka returned from the latrine and handed the book to Kyojuro, the latter's expression changed immediately.
"This is... the book Father often reads?" Confusion and shock mingled in his voice. He could not understand why his father would give this volume—one he rarely let out of his sight—to Asuka.
Asuka placed the book carefully between them. "He threw it at me. Said we should read it instead of wasting time on Flame Breathing."
"...I see." Kyojuro's expression turned solemn as he gently opened the ancient red cover.
A heavy scent of aged paper and mildew rushed out.
The first few pages were written in old but neat script, recording the lives and achievements of past Flame Hashira, along with descriptions of the early form of Flame Breathing.
But after turning more than a dozen pages, Kyojuro's fingers froze.
The pages were no longer continuous.
Large sections had been torn out in an extremely crude manner, leaving the contents inside incomplete and unreadable.
"This..." His gaze trembled in disbelief. "How could this be? Was it Father who destroyed it?"
The torn edges were jagged and uneven, vast blank spaces glaring painfully against the remaining text.
Some chapters had vanished entirely. Others were ripped away mid-narrative, critical passages missing, sentences cut off abruptly.
This was not merely damage to family history—it was desecration of the lifeblood of generations of Flame Hashira.
As Kyojuro's trembling fingers turned the next page, Asuka's sharp eyes caught something unusual.
"Wait."
He reached out and noticed a scrap of rough paper tucked into the edge of one torn section.
Coincidentally, similar scraps were hidden within other ripped portions as well.
These pieces were folded and wedged inside, made of paper entirely different from the book itself.
When unfolded, they were covered in twisted strokes and hurried handwriting. The ink varied in shade, as if the writer had paused for long stretches, uncertain what to write next before continuing.
Under their gradually tightening and bewildered gazes, Asuka and Kyojuro looked at one another and finally realized that these scraps contained parts of the missing chapters.
Most of what they recorded were notes from previous Flame Hashira regarding the original Breathing.
As well as a dialogue between a Flame Hashira of the Warring States era—and a certain special individual.
Yoriichi Tsugikuni.