Nine days later, in the second-stage wind zone of Wind Valley.
Uzumaki Naruto stood amidst a gale of at least level eight, his breathing completely unaffected despite the violent winds blasting directly against him.
He tightly gripped his blade and swung it upward with force. A wind blade surged from bottom to top, tearing through the sky and cleanly splitting the gale all the way to the end of the wind current above the valley.
Not only that—along the path of the wind blade, faint black sword energy erupted and spread, tearing through the air itself and distorting the vacuum in its wake.
This was Wind Breathing, Sixth Form — Black Wind Smog.
"Finally… I did it!"
As the gale surged back over his body, Uzumaki Naruto wore a triumphant expression.
Shinazugawa Sanemi's requirement for Naruto's second-stage training had been strict: Naruto had to master Total Concentration: Constant within the second-stage wind zone while also learning and skillfully applying Wind Breathing's Fourth through Sixth Forms.
The standard for "skillful application" was equally harsh—every sword swing had to split all of the gale within the second-stage wind zone.
Wind Valley's second-stage zone spanned fifty meters, giving it a radius of twenty-five meters.
In other words, Naruto had to split at least twenty-five meters of gale with every swing of his blade.
He completed this stage of training in just nine days.
"Oh? We have a guest?"
Emerging from the valley, Naruto spotted a figure standing beside Shinazugawa Sanemi—someone wearing a Hannya mask.
After a brief moment of surprise, Naruto immediately reacted with excitement.
"Is that the swordsmith?"
"Yes."
The masked man nodded. "My name is Titanium. I am the swordsmith responsible for forging your nichirin blade."
Titanium removed the bamboo basket from his back and took out several pieces of ore, placing them before Naruto.
"Uzumaki Naruto-dono, please choose one of these ore pieces. It will be used to forge your nichirin blade."
In truth, Titanium had arrived three days earlier, but Naruto had still been training in Wind Valley, so Shinazugawa Sanemi had him wait.
"Oh."
Naruto stepped forward, carefully examining the ore pieces before asking curiously, "Are these ores different from each other?"
"There is little difference," Titanium replied. "They were all collected from mountains closest to the sun and have absorbed sufficient sunlight.
The reason you must choose personally is to determine compatibility. This allows us to forge a nichirin blade best suited to you. Simply choose the one that feels most comfortable by intuition."
"I see."
After observing the ores for a moment longer, Naruto pointed decisively.
"This one."
"Understood."
Titanium set the chosen ore aside, then produced a measuring tape and approached Naruto.
"Which hand do you usually wield your blade with? I need to measure your dominant arm."
"My right hand."
Naruto switched his sword to his left hand and extended his right arm.
After completing the measurements, Titanium asked, "Do you have any requirements regarding the style of your nichirin blade?"
"Style…"
Naruto thought briefly, then shook his head. "No special requirements. As long as it's easy to use."
He had once considered forging a weapon like Kaido's spiked club—Kaido's blow had left a deep impression on him—but Wind Breathing clearly did not suit such a weapon.
"Please rest assured," Titanium said confidently. "I will forge the most suitable nichirin blade for you."
"Forging will take approximately ten days. Once completed, I will personally deliver it."
"Thank you for your trouble."
Naruto bowed slightly in gratitude.
"It is my duty."
Titanium returned the bow. "The necessary data has been collected. I will take my leave."
"Mhm. See you next time."
Naruto waved as the swordsmith departed, then turned eagerly toward Shinazugawa.
"Shinazugawa, I've completed the second stage. Are we moving on to the third stage now?"
Shinazugawa Sanemi glanced at him, nodded, and drew his nichirin blade, immediately beginning to demonstrate the final three Wind Breathing forms.
As for the original goal of having Naruto endure one hour in the third-stage wind zone within a month, Shinazugawa pretended it had never existed.
Ten days later.
"Naruto."
Shinazugawa Sanemi entered Wind Valley, stopped before Naruto, and drew his blade.
"Your training is sufficient. Now, I will spar with you."
After twenty-five days, Naruto had completely mastered Wind Breathing's techniques and sword forms, and his Total Concentration: Constant was exceptionally stable.
His strength had fully reached the level of a Hashira.
The only thing he lacked now was real combat experience.
Shinazugawa Sanemi intended to use the remaining five days of his leave to address that deficiency.
"Oh!"
Naruto instantly understood and took a fighting stance, eyes blazing with excitement.
The two began their fierce sparring amid winds exceeding level ten.
Five days later.
After completing their training, the two exited the valley, where a black-clad figure wearing a face mask awaited them.
This person was a member of the Kakushi, the Demon Slayer Corps' cleanup unit responsible for post-battle operations.
He had come to deliver intelligence Shinazugawa had requested from Master Ubuyashiki Kagaya half a month earlier.
"Shinazugawa Sanemi-sama."
The Kakushi stepped forward and respectfully presented a thick envelope with both hands.
"Master Ubuyashiki Kagaya has approved your request. This intelligence contains all currently known demon sightings, as well as suspected locations of the Twelve Kizuki."
"Good. I understand."
Shinazugawa accepted the envelope.
"Please convey my thanks to Master Ubuyashiki Kagaya."
"Yes, Shinazugawa-sama!"
The Kakushi bowed deeply, then quickly departed.