Having fled for more than ten kilometers, the scattered pieces of Muzan's flesh began to squirm and coalesce in a forest, eventually forming a mass the size of a human head.
Just as the sun was about to rise, Muzan burrowed deep into the earth.
As long as he wasn't exposed to sunlight, he wouldn't die. No matter how much power he lost, he could slowly recover.
"Muzan, I know you're hiding here. You can't escape."
A calm voice drifted down from above. Uchiha Nagi had followed him.
What? How does he know I'm here?
"Grand Sand Mausoleum..."
The earth began to contort, the surrounding soil dissolving into sand. Muzan, still hidden within, was forcibly dragged out in a state of utter confusion.
"How did you find me, you human...?" Muzan asked, his face a mask of disbelief. In response, Nagi simply pointed a finger to the sky.
"AAAAAHHHH...!"
The first ray of sunlight had struck Muzan's body. His flesh immediately began to burn and smoke. He howled in agony, all thoughts of questions forgotten. His only instinct was to burrow back into the ground to escape the light.
However, the soil was now firmly under Nagi's control. Even if Muzan managed to dig in, he was immediately forced back out.
To slow his own disintegration, Muzan used the last of his strength to activate a final Blood Demon Art. He transformed into a giant, grotesque infant.
[It was you. This was all your doing!]
With nowhere to go and no escape, Muzan lunged at Nagi in a final, desperate gamble.
[I finally see the truth in Kagaya Ubuyashiki's words. The will of humanity is what's truly eternal. And today, you will become the vessel for my dream! You will become the next Demon King!]
The giant infant's body enveloped Nagi, and Muzan began pouring all of his power and consciousness into him. He didn't possess a technique like Orochimaru's Living Corpse Reincarnation; his method of "possession" was more like a complete transfer of power, akin to a master passing their entire life force to their disciple.
By accepting Muzan's power, Nagi would become the new Demon King, just as Tanjiro almost had. A perfect Demon King, a flawless being who did not fear the sun.
But Nagi hadn't grown up eating Red Spider Lilies like Tanjiro's family had. He wasn't sure if he could gain an immunity to sunlight, so—
[Muzan, I think you've misunderstood. It is I who will be devouring you, not you passing anything on to me.]
In the mindscape, Nagi opened his Mangekyo Sharingan. In the next instant, the Uzumaki clan's Adamantine Sealing Chains, layers of fuinjutsu, and Shukaku's pyramid seal erupted from all directions, binding Muzan's power completely before sealing it away in the depths of Nagi's consciousness.
[Hahahaha! Muzan, I'll be taking your power. As for your soul, please do me the favor of dying peacefully.]
Nagi covered his face and let out a wild laugh. He had planned this for so long. Secretly planting a Flying Thunder God seal on Muzan's body, letting him escape, forcing him into a corner with the Hashira—it was all to ensure the outcome was the same as in the original story, to make Muzan surrender his power.
To gain Muzan's power only to immediately abandon it and take the cure, as Tanjiro had done, was an incredible waste. Nagi's plan had always been to claim the power of the Demon King for himself.
As for Muzan's soul? A soul wielding the Mangekyo was a master of the spiritual domain. Muzan stood no chance of possessing him. Besides, judging from the original ending, Muzan didn't even have a possession technique. Otherwise, he wouldn't have abandoned his own body to give all his power to Tanjiro.
In the mindscape, Muzan was silent for a moment. Then, he actually began to laugh.
[Heh heh. You chose to keep my power. That means my legacy will not be broken. My will—the eternal dream of a perfect being—will continue to exist in this world.]
[Kagaya Ubuyashiki, you have won. But so have I. Hahahahaha...!]
Nagi was speechless.
With a final, booming laugh, Muzan calmly accepted his death. His body disintegrated into ash under the morning sun.
"Nagi-nii, are you okay?"
"Nagi-sensei—"
"Nagi-san?"
"Plum-blossom-eye-aniki! You didn't turn into a demon, did you?"
"Inosuke, you boar-head, don't say such unlucky things!"
Guided by the Kasugai Crows, the Demon Slayers arrived at the small forest. All they saw was the remains of the giant infant turning to ash in the sunlight. In its place stood Uchiha Nagi, his eyes closed.
Slowly, Nagi opened his eyes. The plum blossom pattern of his Mangekyo was still there. And on his forehead, the empty rune that once held the Ryumyaku's energy was now full again, taking the shape of a third eye. Stored within was the power of Muzan.
A power of immortality akin to Tsunade's Creation Rebirth, but a hundred times stronger.
Nagi looked at the concerned faces of the Demon Slayer Corps members and smiled. "I'm fine. Muzan has been eliminated."
"Really? Hooray! Muzan is gone!" The first to cheer was Inosuke. He tore off his boar mask and threw it high into the air.
"That's great... that's really great... hic..." Kanao, who had never been able to cry due to her emotional trauma, finally broke down in tears.
The Stone Hashira's tears flowed even more freely. He pressed his palms together and quietly chanted, "Namu Amida Butsu..."
With their protagonist-level senses, Zenitsu, Tanjiro, and Inosuke could all feel it. Muzan's presence had vanished from the world. Completely.
Muzan was really dead.
Seven days later, at the Butterfly Estate—
Kiriya Ubuyashiki, only twelve or thirteen years old, gathered all the members of the Demon Slayer Corps, accompanied by his two younger sisters. The meeting included the support staff, the retired Flame Hashira Kyojuro Rengoku and Sound Hashira Tengen Uzui, and the heavily injured but now recovering Shinazugawa brothers and Shinobu Kocho.
"Everyone, on behalf of the Ubuyashiki family, I offer you our most sincere gratitude." Kiriya's voice was thick with emotion as he knelt before them, his twin sisters kneeling beside him.
"You mustn't!" "Young Master, please rise." "There's no need to thank us! It was our duty..."
Nagi stepped forward and helped the weeping boy to his feet.
Kiriya wiped his tears and managed a smile. "Now that Kibutsuji Muzan has been eliminated, I have a momentous announcement to make."
"The Demon Slayer Corps... is hereby disbanded."
"What? The Demon Slayer Corps is disbanded?" "Disbanded? Then what will we do?"
"Muzan is dead, so no new demons can be born. We will hunt down the remaining ones, but their numbers will only dwindle. Disbanding the Corps is the natural course of action," Kiriya explained, his voice still choked with tears. "The support teams will continue to operate for some time. If any remaining demons are found, we will notify you. But I believe that without Muzan, the rest will not be able to cause much trouble."
The group was filled with a mix of joy and sorrow. Joy that Muzan was finally gone, and sorrow for the impending separation. After spending so much time together, they had all formed deep bonds.
After the Hashira had said their bittersweet goodbyes and dispersed, Kiriya and his sisters approached Nagi and bowed deeply.
"Nagi-san, thank you so much for saving my two sisters."
"There's no need to thank me," Nagi said, helping the children up. "I'm only ashamed that I couldn't change your mother's mind..."
"I know," Kiriya said sadly. "Mother decided to be with Father, in life and in death. It was her decision. We couldn't change her mind."
Nagi sighed. He had tried to persuade Lady Amane, but her will was set. She was determined to follow her husband, and there was nothing he could do.
"Nagi-san, you destroyed Muzan. The Ubuyashiki family can never repay you. If there is anything you need from us, please, do not hesitate to ask."
Nagi thought for a moment. "In that case, I won't be polite. I'd like to ask about the locations of this country's major military bases..."
"Of course," Kiriya agreed without a second thought. Whatever Nagi planned to do, it didn't matter. Muzan was dead, and the curse on their family was broken. Compared to such a monumental favor, a little intelligence was nothing.
Kiriya promised to deliver the information the next day. After bidding him farewell, Nagi went to the infirmary at the Butterfly Estate.
The Flame and Sound Hashira had already left. The Love Hashira and Serpent Hashira had shyly run off somewhere together.
The only ones left in the infirmary were the recovering Shinazugawa brothers and the trio of protagonists, who had nowhere else to go, being orphans.
"Ah, Red-eye-aniki is here!" Inosuke was the first to spot Nagi. He wasn't wearing his mask anymore.
"Nagi-nii, you're just in time!" Tanjiro said happily. "We were just talking about where to go. Zenitsu and Inosuke are planning to come live with us on our mountain. Would you like to come with us?"
His sister, Nezuko, was human again. With their revenge complete, the siblings planned to return home for a while.
Nagi smiled. "I won't be joining you. I'm planning to return to my hometown. I still have things to do there. I came to say goodbye."
"Oh, is that so... Well, Nagi-nii, you have to come visit us often, okay?" Zenitsu said, a little sad. It was thanks to the Lightning Release Armor training Nagi had taught him that he had been inspired to create Honoikazuchi no Kami and defeat his senior in a single blow.
Suddenly, an unexpected voice spoke up. "Sensei, can I go with you?"
Nagi turned to see the Shinazugawa brothers. It was the younger brother, Genya, who had spoken. He was still recovering from his injuries. His older brother, Sanemi, stood to the side, cradling his sword.
"Don't look at me," Sanemi said nonchalantly. "He's not a kid anymore. He makes his own decisions. I can't interfere, just like when he decided to join the Corps in the first place."
Nagi looked at Genya seriously. "My hometown... there may be no demons, but the fighting there can be even more brutal. Are you sure you want to come with me?"
Genya nodded firmly. "Yes, I've made up my mind. I want to become stronger. Even though Muzan is gone, I feel it would be a waste to abandon my unique talent. And you, Sensei, are the only one who can help me."
Nagi smiled and nodded. "Alright. As long as you've decided. Get ready, we leave tomorrow."
"That's great!"
His older brother, Sanemi, cracked a smile at Nagi and nodded before walking out. His grin, however, was still a bit terrifying.
"Since we're all about to part ways, let's have a big dinner tonight! Let's eat and drink until we drop!"
Shinobu appeared at the door, smiling, with Kanao and the three little girls from the Butterfly Estate in tow.
"Yeah!" "Yeah, what? Children can't drink." "What does it matter?" "Crab-jiro, is alcohol good?"
That night, they all gathered around a bonfire, cheering and celebrating. Nezuko performed a mountain song and dance from her village, completely captivating Zenitsu and Inosuke.
Two unexpected guests also arrived: Tamayo and Yushiro. They had taken the cure and become human, meaning that in a hundred years, they too would age and die like everyone else.
They sang and danced, some performing, others joining hands to dance around the fire.
Amidst the celebration, Nagi took Shinobu up to the roof, just as they had done the first time they watched the moon together.
"This is for you," Nagi said, handing Shinobu a scroll.
"What is it?"
"You turned yourself into a living poison. While the wisteria toxin is harmless to humans and lethal to demons, you have too much in your system. If you don't slowly purge it, your life will be cut short," Nagi explained. "The medicine inside is a mixture of White Zetsu cells and cells from Genya's demon-eating body. I've already prepared the correct proportions. Just use it, and you should be back to full health soon."
"Thank you..."
Shinobu accepted it with a gentle smile that bloomed like a flower. This was her true self. After giving Doma his just deserts and sending him to hell, her wish had been granted, and she no longer had to wear a mask.
"You're leaving tomorrow? Will you come back?"
"Yes. I'm not sure when, but once things are settled over there, I'll visit often."
"Really? That's wonderful. I was worried I might not see you again."
"You will. After all, Genya will be with me. He'll have to come back here eventually," Nagi said with a smile. He was taking Genya with him whole, and he would certainly bring him back whole. He was also curious to see how far the demon-eating boy could go in the ninja world.
"You've given me such a life-saving gift. I don't know what to give you in return," Shinobu said, looking down at the scroll in her hands.
"You already have. The Red Spider Lilies at the Butterfly Estate are beautiful. I've collected several varieties," Nagi answered with a smile.
Shinobu thought for a moment, and a faint blush crept up to her ears. "Close your eyes. I have a gift for you—"
Nagi blinked, then closed his eyes as if he understood. She didn't know, of course, that he had mastered the Transparent World. He could see everything around him perfectly, even with his eyes shut.
Mmm...
His lips met something as soft and sweet as cotton candy. A long moment later, a voice, barely a whisper, sounded by his ear.
"Come to my room... so they don't find us."