After Ryoma and Tanjiro got used to such intense training, Sakonji officially began teaching them the Breathing Style.
Breathing Style was a skill developed by Yoriichi, created to allow ordinary humans to fight demons with their flesh and blood.
It primarily strengthens cardiopulmonary function through breathing, allowing one's blood to absorb a large amount of oxygen in a very short time, thereby significantly enhancing one's physical abilities and enabling humans to possess the physical strength to contend with demons.
Different Breathing Styles have different characteristics, but continuously using Breathing Styles places a very severe burden on the body.
This is why Sakonji first spent a lot of time improving their physical fitness before starting to teach them a Breathing Style.
When one trains to the point where they can operate the Breathing Style with full concentration even while sleeping, they have entered a higher level—Total Concentration: Constant.
Thoroughly mastering Total Concentration: Constant is the minimum requirement to approach the strength of a Hashira.
Sakonji began to guide them step by step in changing their breathing methods.
"Upper body relaxed, lower body stable and still, good, breathe."
Ryoma could easily sense the difference in breathing methods and adjusted quickly, but Tanjiro struggled, constantly trying various breathing patterns but failing to grasp the key, which prompted Sakonji to hit his stomach several times in frustration.
Although Ryoma could adjust, he temporarily didn't feel any increase in power, so it seemed that simply doing this wasn't enough.
For Water Breathing, Sakonji took them to the bottom of a waterfall, letting them experience the flow of water and merge with its essence.
Boom!
The surging waterfall was like a water dragon, roaring as it smashed onto Ryoma's shoulders and back. Every drop of water seemed to possess immense force, threatening to shatter his bones.
He gritted his teeth, his legs deeply submerged in the icy stream, maintaining his sword-swinging posture, the muscles in his arms long past soreness, entering a burning numbness.
It had been a year.
Since stepping onto Mount Sagiri, day after day of extreme training had already honed him like a stubborn rock.
Sakonji had taught them all the knowledge he could impart. The rest was up to them to comprehend on their own.
Sakonji led Tanjiro to a boulder as tall as a man and told him that if he could cleave it, he would be allowed to participate in the Final Selection.
Despite thinking it was impossible, Tanjiro picked up his sword and began his attempt.
Sakonji then turned to Ryoma, telling him to practice his swordplay directly under the waterfall.
Over the past year, Tanjiro had managed to grasp the basics of Water Breathing under Sakonji's angry shouts and blows. Ryoma, however, remained stuck outside the gate.
Ryoma had a good grasp of everything else, but he lacked in the Breathing Style, which was the most crucial aspect.
His perception could easily discern the principle of the Breathing Style changing the heart and lungs and stimulating blood, but he just couldn't do it.
Whenever he tried to guide that aura, the magic power circulating within him would produce silent resistance, like loose sand. No matter how the torrent of breath washed over it, it could not be condensed.
This power from another world had become his greatest shackles.
The only thing he could feel was that with each extreme breath and sword swing, the dormant magical dust deep within his body seemed to have an extremely faint, almost illusory... tremor?
There was a vague illusion that something was about to break free.
"Hoo... Hoo..."
After another sword swing, Ryoma finally couldn't hold on, staggering out of the waterfall's impact range, leaning on his sword and panting heavily.
Water droplets slid down his pale cheeks. He wiped his face, and his raised eyes inadvertently glanced into the distance.
Deep in the forest, on the giant rock that Tanjiro challenged day and night, a figure sat silently.
He wore a fox-patterned mask similar to Sakonji's, had neat short hair, and a tall, straight figure. He vaguely seemed to be non-corporeal, surrounded by a faint glow that almost merged with the air.
A soul.
Ryoma's breathing instantly stopped. He could "see". He could clearly see that existence that should not be seen by the living.
Sabito...
This name, and the story related to him, instantly flashed in Ryoma's mind.
During the Final Selection, Sabito, to protect others, killed all the demons on Mount Fujikasane except the Hand Demon, and thus encountered the Hand Demon who had killed several of Sakonji's disciples, ultimately dying at its hands.
Ryoma knew that the souls of Sabito, Makomo, and other disciples of Sakonji had returned to Mount Sagiri, and he also knew that during this period, they would appear to guide Tanjiro.
But Ryoma didn't expect that he could also see them. This was his first time seeing and truly feeling the existence of a soul.
"This world... Indeed, death doesn't necessarily bring peace."
Ryoma looked up again in Sabito's direction. That figure seemed to have noticed his gaze, turning his head slightly, and through the mask, his eyes seemed to meet Ryoma's for an instant.
No words were spoken, yet it conveyed more than a thousand words.
A current shot up Ryoma's spine to the top of his head. He took a sharp breath and refocused his attention on himself.
If Water Breathing is a skill for guiding "water flow," then what is the magic within me? Is it a stubborn rock obstructing the flow, or... another hidden undercurrent beneath the riverbed?
He turned and walked back under the cold waterfall, closing his eyes.
This time, he no longer forced himself to imitate the rhythm of Water Breathing, but instead immersed his entire spirit within his body. He imagined himself as the endlessly flowing stream, and those magical dust particles as the sand at the bottom of the water.
"Hoo—"
As he inhaled, he drew out an invisible force, gently rolling up the dormant magic power like flowing water.
As he exhaled, he infused this "force" and magic into every muscle tremor, every sword swing.
This time, the feeling was completely different.
The incompatible magic power within his body, for the first time, yielded to his will. A strange energy, as if formed by the fusion of extremely cold ice springs and his own magic, instantly flowed through his limbs and bones, dispelling all fatigue and bringing an unprecedented, bone-chilling clarity.
Just then, the training sword he tightly held suddenly felt unusual.
Buzz!
The training sword in his hand emitted a clear, high-pitched hum. A visible layer of light blue frost, like condensed moonlight, instantly spread from the hilt to the blade.
Crack!
A faint but crisp sound of freezing echoed.
Ryoma could see that at the tip of the blade, where the light blue magical aura covered it, a layer of crystal-clear thin ice condensed and spread out of thin air at a visible speed.
It was no longer just a watery aura covering the blade, but rather a tangible change in the state of matter.
At the tip of that blade, a massive cold air gathered, and the water vapor in the air was instantly frozen and shaped.
A three-inch long, crystal-clear ice blade, emanating a chilling cold, appeared out of thin air.
The "form" of Water Breathing and the "quality" of his magic finally merged at this moment, producing a strange transformation.
Ryoma also discovered that this transformation not only endowed the blade with ice power but also completely changed the essence of his magic.
The originally dust-like, unaligned magic power now seemed to be imbued with the spirituality of water and the crispness of ice, possessing distinct water and ice characteristics.
He could now use magic power to condense ice blades and water blades for attack, just like the demons of this world use Blood Demon Arts.