"Your own thirteenth form…?"
Yoriichi muttered as he watched the change in Riezel's expression.
In fact, just like Riezel had said, he had always thought that the thirteenth form he created couldn't really be considered a new sword form. It was merely a cycle formed by the twelve forms of Sun Breathing, which anyone who could use the first twelve forms could accomplish.
Given this, how could it be considered a new sword form?
For this reason, even though he created this so-called thirteenth form during his encounter with Muzan, he never named it. In his eyes, it was just an application of the twelve forms of Sun Breathing.
He had indeed considered creating a truly new sword form, but the idea was fleeting.
It couldn't be helped.
After all, he had just finished his once-in-a-lifetime battle with Muzan, which ended with Muzan's escape, leaving him with a lifetime of regrets.
Moreover, to make matters worse, not only had his own brother fallen and become a demon, but he had also killed the Master they had served, resulting in his banishment from the Demon Slayer Corps and leaving him completely isolated.
In that kind of situation, how could he have the mind and leisure to create a new sword form?
However, the young man before him seemed to have achieved something that he never could in his lifetime.
*Click*
Under Yoriichi's gaze, Riezel slowly sheathed his sword, placing Hermit back in its scabbard.
However, not only did the blazing flames swirling around his body not extinguish, but they also became even fiercer and more intense, wrapping around Hermit at his waist.
Soon enough, as if compressed into the scabbard, all the flames around him were absorbed into it.
Riezel lowered his body, one foot forward and the other back, assuming a charging stance. He gripped the scabbard in one hand and the sword hilt in the other.
Seeing this posture, Yoriichi immediately realized.
"Iai?"
Iai, or Iaijutsu, was the art of drawing a Japanese sword, a technique that increased the power and speed of a slash by utilizing the friction of drawing the sword to achieve a kill in one strike.
In fact, the first form of Thunder Breathing, known as the fastest and most explosive of the five fundamental breathing styles, 'Thunderclap and Flash', was also an Iai technique.
At this moment, Yoriichi wondered if Riezel's true thirteenth form could also be an Iai technique.
'I see, so that's why he said one final strike...' Yoriichi thought to himself.
Iai naturally involved only one strike since it aimed for an instant kill—one strike to defeat the opponent and one strike to win.
Once the sword was drawn, there was only one slash.
If it failed, there were no follow-up moves.
In other words—
'As long as I can block this strike, I win.'
Yoriichi immediately lowered his body and gripped his sword with both hands. At the same time, the transparent sheen in his eyes grew more intense.
At this moment, Yoriichi pushed the Transparent World to its limits.
'See through it!'
Yoriichi's mind was consumed by this single thought, but soon enough, he felt a sudden shiver run through his body.
He realized that Riezel's breathing intensity had suddenly risen several levels. He could feel that the air absorbed into Riezel's lungs transformed into strength, flowing into his limbs, organs, and every cell, causing the power within his body to surge several times!
*Whoosh!*
Suddenly, as a surge of flames erupted from Riezel's body, they flowed toward the sword at his waist, pouring into the scabbard, and making it emit a sharp whine.
Before long, the intense heat and pressure instantly exploded from Riezel's body, sweeping in all directions like a hurricane.
"Sun Breathing - Thirteenth Form…"
Riezel's voice seemed to come from within the sun itself, quietly appearing.
Flames burst forth, the fire crackled, and the entire world felt as though it were being dragged into the center of the sun, with violent tremors and flickering.
At this moment, in Yoriichi's Transparent World, only a bright sun seemed to rise before him.
In the next second, a figure and burst of fire emerged from the sun, occupying his entire field of vision and all his senses.
In a daze, the figure in the flames began to draw his sword.
However, not only did the sword feel as if it could evaporate everything with its searing heat, but its strike also seemed to compress the sun itself into its fiery red blade.
In an instant, the extreme heat, the peak slash, flashed through Yoriichi's Transparent World.
By the time Yoriichi came to his senses, the scene had changed back to the mountain, now turned into a sea of flames.
Soon, Riezel's voice softly came from behind Yoriichi.
"Blooming Radiance..."
As Riezel's voice fell, the burning Hermit was slowly returned to its scabbard.
*Click*
"..."
With the clicking sound of a sword meeting its scabbard, time seemed to freeze in that single moment.
Yoriichi stood in a daze for a long time, silent.
After a while, he finally parted his lips and spoke slowly.
"Well done…"
*Crack!*
As soon as Yoriichi finished speaking, the sword in his hand broke.
If someone saw his broken sword, they would notice that the fractures were surprisingly marked with reddish burn traces.
*Splurt!*
At the same time, a gush of blood suddenly spurted from Yoriichi's front, revealing a deep wound that extended to the bone. Not only did this wound nearly split him in two, but it also drenched his entire body in blood.
"Huff..."
Riezel exhaled the long-held breath from his lungs, standing there, unable to move any longer. Upon closer inspection, his whole body was trembling, every muscle twitching, clearly unable to continue fighting.
It couldn't be helped.
'Sun Breathing - Thirteenth Form - Blooming Radiance' was the thirteenth form of Sun Breathing created by Riezel, the final sword form, the strongest sword form, and the ultimate strike with only a momentary radiance.
"In that brief moment just now, you not only used Sun Breathing to strengthen your body but also took it a step further, squeezing every bit of power from your entire being and making your strength increase several times in that instant, right?"
Yoriichi, covered in blood and seemingly unaffected by pain, spoke with his back turned to Riezel.
"Yeah..."
Riezel replied without turning to look at Yoriichi—or rather, he no longer had the strength to do so.
"By intensifying my breath for just a moment, I concentrated all the power I had in my body to explode at once. In this way, I could maximize my strength output, allowing me to increase my power several times in that instant."
"But after that, my body wouldn't be able to move."
"That's why I said I could only strike once—one final strike."
Riezel developed this final strike into an Iai technique, pushing its power to the extreme.
Not only did the power unleashed in that instant increase his physical abilities several times, but it also amplified the power of Sun Breathing. He compressed all the flames from Sun Breathing that erupted in that state into Hermit's scabbard.
In this way, the temperature of Hermit's blade would rise again, increasing its power, and the speed of the sword draw would also be elevated to an extremely terrifying level, thanks to the force of the flames erupting from the scabbard the moment it was drawn.
Such a swift slash was surprisingly beyond the comprehension of Yoriichi, who had mastered the Transparent World since childhood.
No choice.
Such a mighty slash could even cut through not just ordinary iron but even first-class special equipment from the world of Danmachi.
Riezel's ultimate strike, combining extreme speed and power, left no room for evasion, reaction, defense, or resistance—an ultimate final strike.
It was Riezel's thirteenth form of Sun Breathing—named 'Blooming Radiance'.
"Perfect."
Yoriichi praised without hesitation, then felt it wasn't enough so he added again.
"And flawless..."
Clearly, to receive such praise from the founder of the breathing style himself showed how astonishing the thirteenth form of Riezel's Sun Breathing was.
Yoriichi displayed an unprecedentedly satisfied expression.
"Seeing Sun Breathing bloom with such potential and brilliance at the end of my life, I have no regrets..."
"Blooming Radiance is indeed a very fitting name."
"You will surely use it well."
Yoriichi's tone brightened, losing its previous calm but remaining optimistic.
"..."
Riezel fell silent for a moment, then mustered the last of his strength to turn around and bow to Yoriichi in gratitude.
"Thank you very much for fulfilling my unreasonable request till the end."
Without Yoriichi, he wouldn't have learned Sun Breathing.
Without learning Sun Breathing, he wouldn't have been able to evolve it and attain staggering power that spanned a level, as well as the capability to continuously strengthen himself permanently with the help of 'Total Concentration - Constant', gaining more possibilities for growth.
As such, Riezel's bow was expected and understandable, as it was a gesture of gratitude for Yoriichi's help.
"No need." Yoriichi calmly shook his head. "You took on the responsibility I had unilaterally assigned, making up for my regrets in life. It should be me thanking you, right?"
As soon as he finished speaking, his body began to fade into a ghostly shape.
"Now, I can finally go find my wife..."
Before long, the wounds on Yoriichi's body gradually vanished, shimmering like a mirage, swaying along with the surrounding scenery.
Seeing this, Riezel smiled faintly.
"Don't worry, you and your wife will have a bright future."
"You'll both reincarnate into a peaceful era and meet again, tying the knot once more."
"When that time comes, you'll surely live a safe and happy life."
"I guarantee it."
Riezel's words were not without reason.
After all, this was what happened at the end of the original work.
"Is that so...?"
Yoriichi seemed lost in thought, his expression softening into a genuine smile of happiness as he imagined such a future.
"If it really is that way, then that would be wonderful…"
With these words, Yoriichi finally vanished with a smile on his face.
He vanished along with the dream, slowly disappearing from Riezel's view.