To end the curse that had plagued his family for millennia, he chose the darkest path.

As the 97th Master of the Demon Slayer Corps, Kagaya Ubuyashiki has always been a gentle and revered leader in the hearts of all his members. However, as the curse increasingly erodes his life, and as he foresees that his daughters will repeat the same mistakes, on the verge of despair, he makes a choice that will shake the world—to make a deal with Muzan Kibutsuji and become the most hidden Upper Moon Zero.

By day, he remains the lord who guides everyone in the fight against demons; by night, however, he is loyal to his millennia-old nemesis. When the truth is revealed on the eve of the final battle, the Demon Slayer Corps' faith crumbles overnight. The former "father" becomes the most despicable traitor, and the Pillars who once swore their undying loyalty turn their blades against each other.

But at the end of this sin-soaked road, does Kagaya hold a trump card that can turn the tide for a thousand years? When wisteria blossoms alongside bloodshed, this game of chess that began with betrayal will finally reach a shocking conclusion.

He traveled through time and space and became the younger brother of Muzan Kibutsuji.

For the promise and the responsibility.

Embark on a journey to kill Muzan Kibutsuji.

And during these endless years, more unknown secrets were discovered.

Why are ghosts born? Why can the priests predict the future?

The mastermind behind all this gradually surfaced.

[The First World, Demon Slayer]

【Second World, Naruto】

[Muzan's younger brother + salted fish + no cannibalism + no harem]

He traveled through time and became the Demon King in Demon Slayer: Kimetsu no Yaiba, and the younger brother of Muzan, the comrade-in-arms of Kibutsuji.

He became the second ghost king in the world and found that he didn't need to eat humans, he could become stronger by sucking blood.

Kenjin has no ambitions to begin with, he just wants to get through the plot, marry Kanae Kocho, and absorb some of Nezuko's blood to overcome the sun.

Kenjin, who knew Muzan's character well, was prepared to keep his distance from the despicable Wuzan, but he didn't expect that Wuzan was really despicable.

Muzan: Stupid Ododou, let me devour you, so that I can become the only strongest ghost king.

Kennin: "..."

The otaku died of a terminal illness and took over the body of Kokushibo from the Demon Slayer world.

In order to survive and make up for some of the regrets he had when watching the anime, he decided to become Kokushibo and live in this world...

When Tanjiro Kamado stepped into Nada Spider Mountain, a huge screen appeared in the sky.

The question-and-answer system has officially started. As long as you answer the questions, you can get various rewards, including but not limited to "resurrection", "turning back into a human", "blue red spider lily", etc., to solve your unsatisfactory wishes!

After resurrecting his wife, Akaza said: "I am Fist Pillar. Muzan, I will *your Sage!"

Shinobu Kocho: "I have a gentle personality? Wait until I get the reward and you will know what a killing angel is [sinister smile]."

Agatsuma Zenitsu: "Grandpa was forced to commit suicide? I'll show you what a fucking thunder pillar is! What a fucking thunder pillar is!"

Douma: "The punishment is to experience extreme pain? There's such a good thing?!"

Mitsuri Kanroji: "Eh?! Mr. Iguro likes me? Then I'll confess right now!!!"

Kokushibo: "I want to resurrect Yunichi. Even if Muzan comes, he can't stop me. I said it!"; Muzan: "You are really my living father."

Tomioka Giyu: "I want to be the most popular person [cold face]."

Muzan Kibutsuji: "The reward is a blue Higanbana?! As long as I can get it, I'll do anything~"

......

Is the plot difficult to accept?

Through questions and answers, all of them were changed to perfect endings!

(cp: After chapter 20, I will not promote the official version, only Komare and Snakereen)

Traveling through the world of Demon Slayer, Shigure opens the role-playing system of the universe.

The higher the missions completed and the degree of character restoration, the stronger the power gained.

The first task required at the beginning is Bai'e.

"? Bai'e beats Wuzhan? Doesn't having hands do that?"

[Player progress reaches 15%: Unlock the weapon "Dawn Invasion"]

[Player progress reaches 30%: Unlock the form "Fire Walker"]

[Playing progress reaches 50%: Unlock the form "God of Evil"]

"Nanook... uh no, Muzan Kibutsuji, I bring destruction upon you!"

Muzan Kibutsuji: "No red blade? No markings? Are you also a pillar?"

Shigure: "Pillar?... Pillars are considered pillars."...

Muzan Kibutsuji: "It's useless. Unless I wait until the sun rises, I can be resurrected even if only a piece of flesh is left..."

"I am"

"?"

"The blazing sun will eventually rise!"

This book will further continue the world view with a very high mortality rate. The difficulty of survival for Tanjiro and others will be further increased. The secrets hidden behind the demon king Muzan and a mysterious organization that has existed for a thousand years will be revealed. The story takes place in the second week of the original plot. Li Qingming enters the world of Demon Slayer and obtains the Infinite Achievement System. While killing evil demons along the way, he is also pursuing his inner desires. When making a decision, power and humanity will eventually make a choice.

[System pays for life][Exhilarating combat][Thunderous][Growth]

When Yasui Ryosuke is transported to the world of Demon Slayer, he is devastated.

Good news: He is familiar with the original work and knows the plot.

Bad news: The original owner was a sickly person who was not long for life, and the only cheat was the double-dealing system that required spending a lot of time and effort to become stronger!

"You mean killing demons grants you lifespan, which can then be used to enhance your breathing technique and sword skills?"

Yes, that's right~

How much longer can I live?

[Congenital liver failure, at most one year, haha~]

"Fuck your sister!"

Yasui Ryojie was angry.

What kind of good system would make a cancer-stricken host risk their life?

Knowing the original plot, Ryosuke would never willingly seek his own death by joining the scoundrel Muzan.

If that's the case, then kill!

Kill them until the sky darkens...

Having transmigrated into the world of Demon Slayer, Mugae became Muzan Kibutsuji's adopted son and became Kokushibo's apprentice to learn Moon Breathing. The young prince Mugae declared that with this identity, he could roam freely throughout the entire demon world!

Muzan Kibutsuji: He's such a filial son, I'm dying of filial piety. I never want to kill his father with Tamayo.

Domo: I treat Wuya like a young master. The young master always wants to treat me to wisteria flower tea, and he also likes to take me out to bask in the sun. He's so considerate!

Jade Pot: Young Master Wuya is a hypocrite. He says my pot is asymmetrical, but secretly he sells it for money!

Naruto: With Young Master Wuya's praise and recognition, my flute playing skills are getting better and better!