"Muzan is the obstacle on your path to the pinnacle."
"Hakuji, come back, be yourself again."
"No, not yet, I'm not strong enough. I want to become stronger, to reach the pinnacle."
"And what then, after you reach the pinnacle? What will you do?"
"Me...? Why am I so fixated on pursuing the pinnacle? Ah, right, I want to protect the people I love."
In his dream, Akaza kept repeating these words. Finally, Akaza woke up, drenched in sweat.
"Hmph... hmph... What's going on? Another nightmare. How ironic, for a demon like me to have nightmares~"
This was a cave in a lush, primeval forest. Only demons could survive in such a harsh natural environment.
Since that decisive battle, Akaza had met his master Muzan once, reported the situation, and then came here to train even harder. But Uchiha Nagi's words remained like a lingering shadow, constantly circling in his mind.
Even with eternal life, his fate was at Muzan's whim. How could he pursue the pinnacle like this? Muzan was the biggest obstacle on his path forward... Uchiha Nagi's words were like a needle, deeply piercing his heart. Was Muzan truly an obstacle to his progress?
The thought that his life was forever at his master Muzan's whim made him extremely uncomfortable.
Furthermore, what puzzled and concerned him most was another matter: the two people who appeared in his spiritual world when he was decapitated and on the verge of death after falling under a Mangekyo genjutsu.
That father and daughter gave him an overwhelming sense of guilt and heartache. He was certain it was related to his memories from when he was human.
Hundreds of years had passed, and he no longer cared about his human memories. After all, human memories only spanned about twenty years, insignificant compared to centuries.
But the memory that appeared this time caused him immense heartache. It seemed... it seemed he needed to find something again.
"I'll put my human memories aside for now. But next time we meet, I will absolutely not be decapitated by you again. Absolutely, absolutely..."
Akaza gritted his teeth, punching a nichirin blade stuck in a large tree until it shattered. His hatred for Tanjiro was just as strong, as Tanjiro was the target of the mission Muzan had given him.
Moreover, such a weak person had thrown a nichirin blade and stabbed him as he fled. If it weren't for the sun coming out, he could have killed that weakling with a single punch.
"Damn it, you weakling, how dare you look down on me..." Akaza gnashed his teeth in anger.
---
"Destructive Kill Compass, Technique Deployment—"
At the Butterfly Mansion, Uchiha Nagi was sparring with Tanjiro and the three little ones. He wasn't using his Sharingan, but rather techniques he had copied from Akaza.
He was trying to fight without relying on his Sharingan, even with his eyes closed. Akaza's Destructive Kill Compass was a method that sensed an opponent's fighting spirit, requiring no eyes at all.
"Fighting spirit" was merely how people in this world described body energy, as there wasn't much cultivation of spiritual power here, so most development focused on physical energy.
In their final battle, Akaza was almost decapitated by Tanjiro, who had awakened the Transparent World. This was because the Transparent World involved blending with nature, without killing intent or fighting spirit. However, for his future battles with Itachi, Uchiha Nagi desperately needed this ability.
Facing Itachi, who had honed his genjutsu to its peak, Uchiha Nagi didn't believe his Mangekyo alone could withstand him in the genjutsu domain. The safest approach was to learn more, such as skills that allowed him to perceive opponents and fight without needing his eyes.
The Transparent World was clearly not something he could learn in a short time. Uchiha Nagi had already copied Tanjiro's demonstration of the Kagura Dance Breathing Technique, and he had also copied all of Akaza's Destructive Kill techniques.
Akaza's Destructive Kill was a martial arts cultivation system based entirely on human fighting spirit, and it could be performed without demon genes. However, the last few forms demanded extremely high physical strength.
Because Akaza was a demon, his severed limbs could regrow in a second. Thus, the last few forms were incredibly powerful, and he never considered the limits or burden on the human body, as the after-effects of muscle and blood vessel bursts simply didn't exist for him.
It could be said that Destructive Kill could be used by humans, but also couldn't... Uchiha Nagi could only unleash the first few forms of Destructive Kill. He would only be able to use the later forms once his physical strength increased day by day to a level sufficient to endure them, likely requiring a body as resilient as Might Guy's.
Especially the final move, Destructive Kill: Final Form, which could break Susanoo, surpassing even Morning Peacock.
"Watch me! Water Breathing!"
"Beast Breathing—"
"Thunder Breathing!"
Uchiha Nagi, with his eyes closed, continuously dodged the attacks of the three individuals, then began to retaliate with other techniques. He was trying to integrate those elements into his muscle memory.
"Destructive Kill—Void Style."
This was a technique Akaza used when fighting them, used at long range. By swinging his fists, he launched air cannons whose trajectories were invisible to the naked eye and were very powerful. However, Uchiha Nagi used his nichirin blade instead.
His nichirin blade swung rapidly, continuously unleashing powerful air cannons. The only difference was one used fists, the other a blade.
Tanjiro and the others, encountering invisible, traceless air attacks for the first time, despite their eyes capable of observing subtle details, were all hit and sent flying by Uchiha Nagi's air blades.
Since this was a spar, neither side had killing intent or fought to the death. Tanjiro and the two others were merely knocked backward.
"Amazing! Is this the technique of that guy who wasn't wearing clothes that night? It's completely invisible to the eye..." Inosuke exclaimed, standing up excitedly.
"Yes, Rengoku-sensei was caught off guard and injured because he couldn't see it then," Uchiha Nagi nodded.
"Let's end today's practice here. Tanjiro's injuries haven't healed yet."
Uchiha Nagi still needed to further familiarize himself with and adapt Destructive Kill, transforming it into techniques suitable for himself—the opponent used fists, he would use a blade to unleash them... At the same time, whenever he had free time, he practiced the Kagura Dance, hoping that after a few years of practice, he could awaken the Transparent World, that selfless state of blending with nature.
Uchiha Nagi tried the Kagura Dance, and its power was indeed immense, several times stronger than Water, Flame, or Thunder Breathing. However, correspondingly, every time he used it and then stopped, the backlash came, causing excruciating pain throughout his body.
Currently, without his physical strength being enhanced to a certain degree, using Hinokami Kagura in battle would be like opening the Eight Inner Gates, collapsing after three minutes.