The cells Nagi gave Genya were from White Zetsu and Hashirama. He wanted to see which one Genya could absorb.
"Remember, use the cell solution from test tube #1 first. Only if you're sure your body can handle and digest it should you use #2. If you can handle #1, I estimate you'll be able to release chakra and use various ninjutsu."
Genya took the test tubes with delight. He had long coveted Nagi's various magical ninjutsu, but even though Nagi had shared his chakra seed with them, the amount they could refine was still negligible.
But Genya was different. His demon-eating ability was incredibly unique. As long as he consumed a demon's cells, he not only gained their regenerative abilities but could also use their Blood Demon Arts. This meant that if he could consume White Zetsu and Hashirama cells, he could gain chakra and use Wood Style.
If they could capture Muzan and occasionally cut off pieces of his flesh for Genya to eat, he might even be able to replace Muzan entirely and become the first perfect creature capable of walking in the sun.
Genya immediately drank the contents of test tube #1 and felt the changes in his body with a look of shock.
Nagi nodded, then turned to Tanjiro. "Tanjiro, you will train with me in swordsmanship, to cultivate the original Sun Breathing."
"Yes, sir."
"Zenitsu, I will use my Mangekyo Sharingan to teach you a Lightning Release physical conditioning technique. Although you can't refine chakra right now, many of the concepts are universal. I hope it will help your Thunder Breathing."
What Nagi intended to teach Zenitsu was, of course, Raikage A's Lightning Release, Chakra Mode, and their physical conditioning methods. Zenitsu, having been spurred by the sacrifice of his master, was now incredibly powerful. Nagi believed his talent would soon allow him to create the strongest form of Thunder Breathing on his own. The Lightning Release Chakra Mode and its conditioning would serve as a valuable reference.
As for the little piggy, Inosuke, Nagi was quite fond of this child whose mind was as pure as nature itself. But what should he teach him?
"Red-eyed big bro, what about me? What about me? What are you gonna teach me?"
Nagi scratched his head, a little troubled. None of the techniques he knew seemed to be a good fit for him. What to do? Oh well, he'd just throw something at him.
"Ahem. I'll also teach you the Lightning Release Chakra Mode and its physical conditioning. Oh, and also the Monstrous Strength Fist. You can use it as a reference. It's okay if you can't master them, but you can absorb the useful parts for your own use."
He had shared his chakra seed with all of them, but the amount of chakra they could refine was pitifully small, almost nonexistent. So, he decided to let them experience the techniques and create their own moves. After all, these were the main characters. Apart from Tanjiro, the other three were all exceptionally talented geniuses.
Tanjiro relied on his protagonist plot armor.
"Oh, oh! Thanks, red-eyed big bro!" Inosuke nodded frantically, drooling like a little piglet.
Ahem. Nagi felt a little embarrassed, but he really didn't have any techniques that were suitable for Inosuke.
A few days passed quickly. On this day, a message came from Ubuyashiki. His premonition was very strong. It was likely tonight.
The reason Muzan, the boss, would risk coming over was because of Nezuko. For some reason, she hadn't burned to ash under the sun. Hantengu, one of Muzan's subordinates, had transmitted this scene to his scumbag boss just before he died.
And so, Muzan had gone mad, losing all composure. The perfect creature he had dreamed of, the chance to live under the sun, had finally appeared. As long as he ate Nezuko and analyzed her cells to find out why she was immune to the sun, Muzan could evolve into a perfect being. The "perfect being" here, of course, did not mean the strongest in the world, but an immortal one.
In Muzan's eyes, so what if Yoriichi Tsugikuni was strong enough to kill him with a single stroke? He had still died in less than a hundred years. Only an immortal being like himself was truly perfect.
The original plan was for Ubuyashiki to use his twin daughters and his wife as bait, to die with him to deceive Muzan. Of course, he still had a son and heir, Kiriya Ubuyashiki.
However, Nagi had protested this patriarchal behavior. His two little girls were so cute; how could they be sacrificed so casually? He proposed a change to the plan.
Then there was Tamayo's medicine, the quadruple poison that would prevent Muzan from splitting.
That night, only a sliver of the white moon was visible, as if it knew something unusual was about to happen and had hidden itself away. On the dark mountain, only a few oil lamps in Ubuyashiki Kagaya's courtyard were lit.
A handsome man in a Western suit, exuding a devilish charm, walked in and approached the dying Ubuyashiki Kagaya.
Ubuyashiki was already blind, but the blind seemed to have an excellent sixth sense. He spoke. "Is that you? It's a pleasure to finally meet you, Muzan Kibutsuji."
"Ubuyashiki. What a truly... ugly state you're in," Muzan sneered. He was a handsome man, a self-proclaimed perfect being, and he had always detested ugliness, including among his own subordinates.
"Cough, cough. You've finally come to me. The man our Ubuyashiki clan has been searching for... for a thousand years."
"Amane, what does he look like?" Ubuyashiki could no longer see and had to ask his wife beside him.
"He appears to be between twenty-five and thirty years old. His eyes are plum-red, and his pupils are long and slender, like a cat's..." After Amane's description, Ubuyashiki now had a clear picture of Muzan's appearance.
"The head of the clan that has obstructed me for a thousand years has been reduced to this state. Ugly. How utterly ugly. You reek of a corpse, Ubuyashiki," Muzan said. Although he planned to kill Ubuyashiki, the thought of dirtying his hands on a dying man disgusted him.
"Heh heh. And who do you think I have to thank for this? It is all because of you, Muzan. Your actions have brought a curse from the heavens upon the Ubuyashiki clan. Only by eradicating you can our family be truly free from this curse."
"Absurd. I have killed so many people over the past thousand years, yet I have seen no gods or buddhas come to punish me. Don't blame your own problems on others," Muzan said with disdain. He naturally didn't believe in such ethereal things. He had killed countless people over a thousand years; if there were gods, he would have been dealt with long ago.
The two men, just like that, began to chat like old friends. They were from the same family, and their feud had entangled them to this day. It seemed they had endless things to talk about, and finally, they spoke of dreams.
"I suppose your dream is to achieve eternity. But true eternity is not of the flesh, but of the will. Only a will that is passed down for eternity is truly eternal. Just like the conviction of the Demon Slayer Corps, passed down from generation to generation for a thousand years..."
"Hmph. Absurd. When a person dies, they are dead. What's the use of passing down one's will?"
Muzan was growing impatient. There were only four living people in the entire estate: the two children playing outside, and Ubuyashiki and his wife, Amane, inside. But Muzan felt a growing sense of panic and unease. He wanted to make his move, to kill Ubuyashiki and hurry to find Nezuko.
"Muzan, thank you for listening to me for so long..." Feeling Muzan's hand touch his head, Ubuyashiki smiled. "My death will surely raise the morale of the Demon Slayer Corps to an unprecedented level. Muzan, today, you will accompany me to the underworld..."
"What?" An unprecedented sense of crisis screamed in Muzan's mind. But just as he fled the courtyard, the entire Ubuyashiki estate exploded.
BOOM!
BOOM!
A small mushroom cloud rose from the mountaintop. Who knew how many explosives Ubuyashiki had buried beneath his own estate? To make matters worse, he had added sharp spikes to the explosives, and the spikes were coated with poison.
"How many explosives must that have been? It even created a mushroom cloud. Tsk, tsk." Nagi clicked his tongue in admiration. An explosion of this scale was truly an art. Deidara would have loved this mushroom cloud. But Muzan was surely not dead yet.
Nagi narrowed his eyes. The original plan was to use Yushiro's Blood Demon Art as cover to get close to Muzan and kill him. But Tamayo had insisted on completing the task alone. Like Ubuyashiki, she had long since lost the will to live; only death remained.
And so, a trap of a quadruple poison was now closing in on Muzan.
"Muzan, you didn't expect this, did you? The right hand I plunged into your body contains a medicine that can turn you back into a human. You will die today."
When Nagi arrived on the scene, he saw a beautiful man with a shattered body, pierced through by a pile of thorns. And a beautiful woman with a ferocious expression, Tamayo, had her right hand plunged deep into Muzan's body. At the same time, Tamayo activated her Blood Demon Art, using her own blood to quickly deliver the poison throughout Muzan's body.
"It's you! You're the one who killed your husband and child, yet you keep blaming me, pestering me endlessly," Muzan roared.
At the same time, he activated his ability, intending to absorb Tamayo into his body. He didn't believe for a second that there was a medicine that could turn a demon back into a human. And even if there was, he could break it down and expel it.
Swish—
Just as half of Tamayo's body was being pulled into Muzan and consumed, Nagi teleported between them and cut them apart with a single stroke. Tamayo, with only half her body left, could not die. She stared at Muzan with eyes full of hatred.
"It's all your fault! If it weren't for you, I would never have become a demon! I lost my mind and hurt them! It's all your fault!" Tamayo shrieked madly.
But at this moment, Muzan could no longer be bothered with that. He looked at Nagi with terror, because he saw a familiar swordsmanship, a swordsmanship that had appeared on Tanjiro not long ago. It was Sun Breathing.
"Sun... Sun Breathing..."
The nightmare of a thousand years was deeply ingrained in Muzan's genes. Even his subordinates had been affected by this genetic fear when facing Tanjiro.
"Hah... Sun Breathing, Thirteenth Form..." Nagi took a deep breath, and in an instant, the complete Thirteenth Form was unsheathed.
Although it was night, when its master needed it, the meteorite in the hilt of the Nichirin Blade directly supplied a massive amount of energy, causing the blade to erupt with the solar flames it usually only showed in the daytime, its power multiplied.
After one stroke, Muzan was completely sliced into thirteen pieces. The entire process was as smooth as flowing water, giving Muzan no chance to even react.
"Muzan... is dead?" Tamayo was stunned. The enemy she had longed to kill for a thousand years was dead, just like that? It was hard to believe.
"No, he's not," Nagi said, looking intently. Of the thirteen pieces of flesh, several burst into flames, while others rapidly expanded and then exploded, scattering into countless smaller pieces, trying to escape.
"Damn it!" The thing Nagi had feared had finally happened. Because he couldn't bear to see Tamayo consumed by Muzan, he had acted prematurely, preventing the poison from spreading throughout Muzan's entire body. The pieces infected with the poison burned up, while for the remaining pieces, the scumbag boss activated his Majin Buu ultimate technique: self-destruction and escape.
A single body, split into 1800 pieces... how small would each piece be? In any case, Nagi did his best to destroy the fragments. He didn't have Yoriichi's technique of a thousand forms in one sword, so he could only destroy two or three hundred pieces in a very short time.
At the same time, from deep within the earth, Muzan's stronghold, the Infinity Castle, appeared and immediately took in the few remaining pieces of Muzan's flesh. The moment they entered, Muzan vanished. This was the special ability of the master of the Infinity Castle, Nakime: control over space. Nakime was the most unique of Muzan's Upper Ranks. She had no combat ability but could manipulate space, limited to the Infinity Castle, and could even move the castle underground.
"Damn it! Did we fail?! Sob, why? We were so close! You shouldn't have come to save me! You shouldn't have come!" Tamayo cried, tears streaming down her face like pear blossoms in the rain. Compared to her own life, she wanted to destroy Muzan more than anything.
"Lady Tamayo, don't worry. Although there was a small change of plans, everything is under control. I've invited a helper. When all the Hashira have gathered, we will kill our way into Muzan's stronghold together," Nagi said, comforting her with a smile.
"R-really?"
"Of course," Nagi said earnestly. Just now, he had thrown several Flying Thunder God kunai into the Infinity Castle as Muzan's flesh escaped. Muzan had no idea that something like the Flying Thunder God existed in this world. Right now, he was probably a fleshy tumor, rapidly purging the residual poison from his body.
Defeating Muzan wasn't difficult. The difficult part was killing him. The bastard was a coward. Relying on his immortal lifespan, the moment he encountered a fight he couldn't win, he would flee, using his endless life to wear you down.
Soon, the Stone Hashira was the first to arrive. As per their discussion, he was the only one of the Hashira, besides Nagi, who knew the plan.
The Stone Hashira, Gyomei Himejima, had streaks of tears running down his face as he looked at the ruined estate and the Ubuyashiki family, who had been vaporized without a trace. "The Master... and Lady Amane... are they gone?"
Nagi sighed. "Yes. They were all sacrificed in the explosion."
Gyomei silently clasped his hands together and chanted sadly, "Namu... Amida Butsu..."
He had nothing but respect for Ubuyashiki's wife, Amane. When he had offered to use his shadow clones to transform into the twin girls and take their place as bait, Ubuyashiki's wife, Amane, had smiled and refused. She wanted to be with her husband, wherever he went. At the same time, she had thanked Nagi for being able to save her twin daughters. Although Ubuyashiki hadn't told her the specific plan, as his wife, how could she not have sensed it? For her husband to favor their son over their daughters and drag their daughters to their deaths with him... though she hadn't said anything, she must have been heartbroken.
But now, it was alright. Her daughters didn't have to die.