Tanjiro spent half the day learning from Uchiha Nagi. He managed to grasp the basics, but unfortunately, when he tried to practice, not even a shadow of chakra manifested.
Considering the different systems of their respective worlds, however, Uchiha Nagi hadn't expected Tanjiro to master chakra refining in a single attempt. After all, even in the Ninja Academy, child prodigies who could refine chakra on their first day were few and far between.
"Don't worry, failing the first time is completely normal," Uchiha Nagi said reassuringly. "It took me a whole month to refine my first wisp of chakra back then."
"Eh, really? Then I have to keep trying harder!" Tanjiro said, scratching his head. He then remembered the scene from the previous night when Uchiha Nagi had learned a Breathing Style after seeing it just once... "Oh, right, Nagi-nii, let me demonstrate the Breathing Style for you first."
"Alright, thank you for the trouble," Uchiha Nagi nodded.
"First Form: Water Surface Slash!" Tanjiro shouted, beginning to execute the Breathing Style's sword techniques. "Second Form: Water Wheel!" "Third Form: Flowing Dance!" "Fourth Form: Striking Tide!" "Fifth Form: Blessed Rain After the Drought!" "Sixth Form: Twisting Whirlpool!" "Seventh Form: Drop Ripple Thrust!" "Eighth Form: Waterfall Basin!" "Ninth Form: Splashing Water Flow!" "Tenth Form: Constant Flux!"
By the time Tanjiro had demonstrated the entire set of techniques, he was drenched in sweat.
"This is the complete set of the basic ten forms," Tanjiro said, wiping his brow. "However, each form can be combined with others under different circumstances, so its variations are endless."
For example, he himself had once used the Second Form: Water Wheel in conjunction with other movements to create the Second Form: Improved Water Wheel. Also, the Sixth Form: Twisting Whirlpool, when combined with other techniques, had become the Sixth Form: Twisting Whirlpool - Flowing. And the Seventh Form: Drop Ripple Thrust had been modified into the Seventh Form: Drop Ripple Thrust - Curve. The latter two looked similar, but their differences were actually significant. The original Seventh Form was the fastest thrusting technique among the Water Breathing forms, but it wasn't well-suited for decapitating demons. The "Curve" variation, however, was an applied technique that followed a curved trajectory, ideal for intercepting airborne attacks.
In other words, Breathing Styles weren't just limited to the superficial ten forms. It was more like ten to the power of ten, and if one possessed exceptional talent, they could fuse and re-fuse these ten forms almost infinitely. The ten forms were merely the foundation. Whether one could integrate other movements to execute them depended on individual talent. After all, the more powerful the technique executed, the greater the demand on the user's own cultivation, and composite techniques required even more.
True masters were those who could apply them flexibly, adapting different forms to different combat scenarios. An improved version wasn't always the most suitable.
Uchiha Nagi knew that the current Water Hashira, Giyu Tomioka, seemed to be a person of immense talent, having developed an Eleventh Form, "Dead Calm," based on the original Water Breathing.
Wasn't this exactly what he yearned for? Konoha's White Fang, Sakumo Hatake, though a ninja, was a master of swordsmanship. With a single short tanto, he had struck fear into the hearts of countless shinobi, leading to the saying that one could abandon a mission without penalty if they encountered the White Fang.
The Mangekyo Sharingan was a powerful tool, but Uchiha Nagi was an orphan; obtaining an Eternal Mangekyo Sharingan was impossible for him. Without an Eternal Mangekyo, he couldn't awaken the Rinnegan. Rather than chase that, it was better to specialize in Breathing Styles to strengthen himself.
Seeing Uchiha Nagi fall into deep thought after listening to his explanation, Tanjiro asked cautiously, "Nagi-nii, did you understand all of that? My explanation might not have been very detailed. If only Mr. Urokodaki Sakonji were here, he could definitely explain it much more thoroughly than I can."
"Mm, I generally understood," Uchiha Nagi nodded. He took out his short sword and walked to the center of the clearing. "I'll demonstrate it once."
Following the method Tanjiro had just shown, Nagi took a deep breath and began to perform the Water Breathing forms he had just copied, from one to ten, all without error. However, this was merely mimicking the form. To truly make it his own, he would need continuous practice and refinement later on.
"Sugoi... Nagi-nii, you're too amazing! You learned it just by watching once! That's... that's too strong!" Tanjiro exclaimed excitedly.
"This is just the form. I'm still far behind you," Uchiha Nagi shook his head.
"Oh, but I also feel like something's missing," Tanjiro mused. "Right, could it be because you need to practice underwater? When I was learning Water Breathing, I often practiced near water."
"That's probably it," Uchiha Nagi nodded and stopped. After all, he currently only had one functional arm, which was inconvenient. Once his White Zetsu arm fully recovered in a couple of days, he could begin his training in earnest.
Uchiha Nagi flexed the white arm. The finger joints were already remarkably agile. It was hard to believe that just half a day ago, it hadn't even been his own. He could feel that the bones within had seemingly healed completely, but Nagi knew that was just superficial. It would take a few more days for it to feel perfectly like an extension of his own body.
Unexpectedly, the fusion between his Mangekyo Sharingan and the White Zetsu cells was remarkably perfect, like milk blending with water. In just this short while, the fatigue in his right eye from overusing its dojutsu last night had already recovered by more than half. No wonder Obito could use his Mangekyo without restraint.
The next morning, before dawn, Tanjiro, carrying Nezuko curled up inside a bamboo basket on his back, was bidding farewell to Tamayo and Yushiro. Uchiha Nagi was accompanying him.
He was heading to the Demon Slayer Corps headquarters to meet their leader, Ubuyashiki Kagaya, and formally join the Corps. He wondered if, with his current strength, he would even need to participate in any selection process. Since he was heading in the same direction as Tanjiro, they decided to travel together.
"Take care, both of you," Tamayo said with a gentle smile.
"Take care. We'll meet again," Uchiha Nagi replied.
"Hey, hey, you with the scar on your head, don't you dare die!" Yushiro chimed in from the side.
"Mm, please take care as well. I'll do my best to collect blood from all the demons I encounter," Tanjiro said, waving at them before setting off with Uchiha Nagi.
Uchiha Nagi was also filled with anticipation for this journey. He had already learned one of this world's cultivation systems, Water Breathing. As for Sun Breathing, the primordial Breathing Style from which all others were derived, and then awakening a Mark—Uchiha Nagi felt that all things eventually returned to their origin. That might very well be an alternative form of Sage Mode.
The so-called Marks were similar to the markings that appeared on the faces of the First Hokage and Naruto when they entered Sage Mode. Because the complete Sage Mode placed too high a demand on the human body, various different elemental Breathing Styles had gradually evolved later on. It was like how Orochimaru, in his pursuit of senjutsu, had created the Cursed Seals, simplifying Sage Mode so that even those with insufficient physical constitution could use a form of it.
In Uchiha Nagi's view, the people who had created the simplified Breathing Styles in this world were truly geniuses. They had made it possible for ordinary people to cultivate power. In the Naruto world, however, no one had ever really tried to improve Sage Mode, resulting in very few individuals being able to use it. In the end, it was Orochimaru who invented the Cursed Seals...
The two cultivation methods were different, but both involved the utilization of energy. Moreover, Breathing Styles clearly tempered the human body. Over years of practice, they could strengthen a person's physique to an extreme degree, similar to the body-tempering secret techniques of the Raikage's clan.