Equivalent exchange. Uchiha Nagi didn't think he was getting the short end of the stick; on the contrary, he felt he had profited greatly. Exchanging ordinary ninjutsu from the Shinobi World for this world's highest cultivation system, Breathing Styles—he had completely come out on top. And he hadn't even handed over any advanced ninjutsu yet, like the Eight Inner Gates, Chidori, Rasengan, Flying Thunder God... Of course, Uchiha Nagi didn't know any S-rank jutsu; the only one he knew from that list was the Eight Inner Gates.
For them, there was no loss. Medical ninjutsu alone was a massive gain. In this world, apart from Breathing Styles, humans possessed no other extraordinary rapid healing abilities, unless it was a Blood Demon Art. Although their medical practices were quite advanced, they were comparable to the world Uchiha Nagi had transmigrated from before—roughly around the World War I era.
The Demon Slayer Corps had a vast logistical staff. Not everyone had the talent to advance to the rank of Hashira, and some who were injured or had less talent would join the support divisions. The Butterfly Mansion was one such place. Though called a "mansion," it was about the size of a small estate, surrounded by wisteria flowers. There were even different varieties, hybrid wisteria cultivated because they were all poisonous to demons. Besides these, there were many medicinal herbs for the Demon Slayer Corps members, treating various external and internal injuries. Members who could use Breathing Styles had bodies far more resilient than ordinary people. As long as they weren't eaten by a demon on the spot, they could generally survive, though some, of course, were left disabled...
"My, my, moshi moshi, Uchiha-san. Can your Palm Healing ninjutsu reattach severed limbs on the spot? What a remarkable technique! It's hard to imagine that humans created this themselves." Inside the Butterfly Mansion, Shinobu Kocho was discussing medical ninjutsu with Uchiha Nagi.
"It's not absolute. After a limb is severed from the body, the cells will rapidly die due to lack of nutrients. It's best not to exceed 24 hours, and keeping the severed limb at a low temperature is optimal. If it exceeds 48 hours, the arm might be semi-functional even if reattached," Uchiha Nagi explained.
"I see. However, I still don't quite understand that chakra. I tried for several hours this morning, but there was no reaction at all."
"Don't rush. Kneading it out within a month is considered normal." Regarding this, Uchiha Nagi had no concrete reference. In the Shinobi World, children generally started learning the basics of chakra kneading at a young age and then naturally succeeded. Children's comprehension varied; some were fast, some slow. It was normal for chakra to appear after a few months or even a year or two. But for adults... Uchiha Nagi truly didn't know anyone who had started learning to knead chakra only as an adult, so he could only lie and tell them that kneading out chakra within a month was normal.
"Speaking of which, I'm curious about your origins, Uchiha-san. The place you come from must be truly magical, to have something like chakra," Shinobu Kocho remarked.
"I come from another world. I arrived here by a twist of fate while being pursued. I, too, am astounded by this world's Breathing Styles," Uchiha Nagi said with a faint smile. "By the way, if you don't mind, you can call me Nagi-nii, just like Tanjiro and the others. I believe I'm a year or two older than you."
Shinobu paused for a moment, not startled by Uchiha Nagi's words, but by his faint smile. His handsome features were instantly seared into her mind. The Uchiha clan's looks had always been top-tier. Even Obito, who was considered to have the plainest looks among them, was still clear-featured and pleasant. And Uchiha Nagi was on par with Itachi and Sasuke, at the pinnacle of Uchiha attractiveness. Shinobu subconsciously blushed. In the Demon Slayer Corps, Giyu Tomioka was considered quite handsome, but compared to Uchiha Nagi, he was several levels below.
"I'll call you Nagi-san. We've only just met; calling you 'nii-chan' feels a bit awkward," Shinobu said.
"As you wish. I'll give you the books related to medical ninjutsu first. If any of the support staff manage to knead chakra, they can learn from these. If they can't understand the books, they can come and ask me." Uchiha Nagi took out a storage scroll, and after opening it—Poof!—a large pile of books appeared after a puff of smoke. This was some of the medical information he carried, not forbidden jutsu. He had already memorized it, so giving it directly to Shinobu was no issue.
"What a convenient item! It can even store things. This also requires chakra to use, doesn't it?" Shinobu looked at the storage scroll with envy. If she had this, she could carry much more wisteria poison in the future.
"Yes, but I don't know if the materials to make storage scrolls can be found here. I'll make a list later and see if the Demon Slayer Corps can find substitutes," Uchiha Nagi said. Storage scrolls were often made from the pelts of powerful beasts possessing chakra, or at least incorporating parts of them. Only then could they have a strong storage function; it wasn't as if some people thought an ordinary piece of white paper could serve as a storage scroll...
After bidding farewell to Shinobu, Uchiha Nagi went to the infirmary in the Butterfly Mansion. The three youngsters were still lying in their sickbeds. Zenitsu's limbs had shortened considerably due to the spider's poison; he had almost transformed into a spider. He was detoxified now, but it would take a long time for him to recover fully. Tanjiro was suffering from the after-effects of using the Hinokami Kagura. The little boar, Inosuke, had severe internal injuries and broken bones. Unless it was a critical situation, Uchiha Nagi didn't plan to use medical ninjutsu to rapidly heal them. Hadn't he seen a ton of injured people in the Konoha Hospital? Natural healing was often better.
"It's good that you three are alright. Rest and recuperate. Once you've recovered, I'll teach you something," Uchiha Nagi said.
"Uchiha-nii." "Nagi-nii." "Oooh~ Red-Eyes-nii~" Needless to say, the one who couldn't get the name right was definitely Inosuke.
"Red-Eyes-nii, what good stuff are you going to teach us~ Is it a Breathing Style?" Inosuke asked curiously.
"No, it's taijutsu. Your respective Breathing Styles are already very complete. What I'm going to teach you is called the Eight Inner Gates," Uchiha Nagi stated.
"The Eight Inner Gates?!" chorused the three.
That's right, the Eight Inner Gates. A technique where the stronger the body, the more powerful the opening of the gates. This technique wasn't some forbidden jutsu; anyone who understood medical ninjutsu could learn it. The difficulty lay in constantly tempering one's physical body. If it was a weakling, even opening the Seventh Gate wouldn't make them that much stronger. But for a strong person, once they opened the Seventh Gate, it was practically world-destroying. Most of the Hashira in the Demon Slayer Corps were already adults. As age increased, bones and meridians gradually set. Even if they trained in the Eight Inner Gates, it would probably be very difficult for them to reach the Eighth Gate. However, for youths who were still developing, training in the Eight Inner Gates would be more effective. Moreover, Uchiha Nagi was also a little curious if they could maintain their Breathing Styles while using the Eight Inner Gates. Uchiha Nagi wouldn't admit that he just wanted to be a "porter" of techniques...