Chapter 9: Infinity Castle. Muzan Kibutsuji

Since that sound of the biwa, Doma had fallen into a strange space.

The houses in the space were intertwined and chaotic, upside down, and the surrounding atmosphere was extremely eerie; this was the Infinity Castle.

The wound on Doma's body that had been sliced open by Zero was slowly healing, but this didn't prevent him from continuing to be serious and smiling.

He looked toward a woman kneeling on a high platform on the other side, holding a shamisen in her arms. Long bangs covered her entire forehead and eyes; that woman was also a demon.

"Aiya~ Sister Nakime, thank you for saving me! Otherwise, I would have been killed by that strange white-haired boy. If I couldn't see everyone then, how sad everyone would be! Don't you think so, Sister Nakime..."

Doma chattered on to himself, completely ignoring whether anyone was listening.

Zing!

Nakime plucked the shamisen, and a wooden door appeared out of thin air beside her. The door opened, and a man in a suit walked out.

His skin was pale, his figure thin, his pupils blood-red and narrow like a cat's, and he had long black hair. He was the progenitor of demons—Muzan Kibutsuji! A demon who had lived for thousands of years.

Muzan stood beside Nakime, high and mighty, his gaze looking down from the high platform at Doma below, revealing no emotion.

"Doma, you are truly pathetic." Muzan's words lacked any emotion, looking at Doma as if his life or death had nothing to do with him.

"Aiya, Master~ how can you say that~ I was just..."

Before Doma could finish his sentence, he was directly interrupted by Muzan.

"Shut up, you useless thing!" Muzan scolded angrily: "You clearly could have killed that female Pillar of the Demon Slayer Corps, but not only did you fail to kill her, you were also made so pathetic by a human who came later and wasn't even a Demon Slayer swordsman. What use are you to me?!"

Calming the anger in his heart, he spoke again: "It seems that Upper Moon Two has become somewhat degenerate! Not only is there no news of the Blue Bianhua, but even a human who isn't a Demon Slayer swordsman could make you so pathetic!"

"Master, the believers of my Wan Shi Paradise Faith are all earnestly searching for the Blue Bianhua~ I believe there will be clues soon..."

"Did I tell you to speak?"

Seeing this, Doma immediately shut his mouth, but his face remained in a cynical, smiling-but-not-smiling expression.

"Remember, I want results, not clues!"

"Nakime, send me back!"

"Yes, Master!"

Zing!

After the biwa sound, a wooden door appeared behind Muzan, and he stepped into it, disappearing from the Infinity Castle.

Doma saw Muzan leave the Infinity Castle, and the wound on his body sliced by Zero had also finished regenerating. He said: "Sister Nakime, send me too..."

Zing!

Before he could finish his sentence, Nakime directly sent him back to the Wan Shi Paradise Faith, as if she had just done an insignificant thing.

After Muzan left the Infinity Castle, he appeared in the study. He had just seen the situation of Zero's battle through Doma's memory, especially seeing the red blade in Zero's hand, and his body couldn't help but tremble.

A figure appeared in his mind, a figure who also held a blade that looked like it was burning, which made him very afraid.

"That person... that person...!!! Damn it! You damn guy, even dead you won't let me have peace! And that white-haired human! Not only is he powerful, but he also has many weapons I have never seen before...!"

"No! I absolutely will not allow anyone comparable to Yoriichi Tsugikuni to appear before me and hinder my plan! Absolutely not!"

Forcing himself to calm down, he then transformed into a woman in a kimono, walked out of the study, left the house he was in, and wandered the streets at night...

Time returns to several days later.

Zero woke up after dawn and left the Butterfly Mansion on his own to get some air. After being tortured by the Kocho sisters and Mitsuri Kanroji all night, he had experienced what it meant for one hour to feel like a century.

It was clearly less than an hour, but he felt like it was a century, passing very slowly.

During this period, he was constantly dressed up by the three women in turns. The mental torture combined with the physical "torture" made him somewhat exhausted, and he fell asleep directly, while Xiao Yue lay on the bed watching the fun.

At this moment, Zero knew what it meant to lose face completely. He, a guy thousands of years old, had actually been teased by a few little girls. All the embarrassment of the past millennium had been lost in this dimensional world.

"Sigh..."

Zero sighed slightly and left the Butterfly Mansion, heading toward the Ubuyashiki mansion. He wanted to collect more information about this dimensional world. The Demon Slayer Corps had been able to continue for so long, so there must be many records. He hoped Kagaya Ubuyashiki would agree.

But even if he didn't agree, it didn't matter; he could just look for information in a quiet place. After all, such things were like secrets and needed to be protected.

Arriving at the Ubuyashiki mansion, he explained his intention to Kagaya Ubuyashiki, who didn't hesitate at all and agreed directly, leading him to the study in his mansion.

Entering the study, he saw rows of bookshelves filled with books. Kagaya Ubuyashiki informed him that every book here recorded the notes left by every generation of Demon Slayer Corps leaders, and he could view them at will.

After Zero thanked Kagaya Ubuyashiki, he began to pick up one of the books to search. When Kagaya Ubuyashiki left the study, he instructed Amane Ubuyashiki to remain there and told her to provide help directly if Zero needed anything.

Just like that, Zero viewed the notes of every generation of Demon Slayer Corps leaders in the study, and he also obtained some information about this Demon Slayer World.

According to the records in the notes, he discovered that an evil demon had appeared during the Heian period in the Neon country, which was the progenitor of demons—Muzan Kibutsuji.

The notes recorded: Before Muzan was even born, he had almost died several times due to his weak body, and was even born into the world as a stillborn baby.

But Muzan relied on his obsession to live and desperately crawled back from the gates of hell, yet he remained bedridden due to a terminal illness before he was twenty years old...

The records in the notes were somewhat incomplete here, and some records about how Muzan Kibutsuji became a demon were not very complete.

"Muzan Kibutsuji... I remember when Xiao Yue and I first came to this world, we had checked the name Muzan Kibutsuji, but I don't seem to know the specific situation very well. I only know that he is the progenitor of demons, an evil demon who has lived for thousands of years... Maybe I can try!"

Zero entered a command into his analysis glasses:

【Search: Information related to Muzan Kibutsuji!】

【Searching... No relevant information obtained yet!】

"Sigh~ as expected, it still doesn't work like before? If I could know what Muzan Kibutsuji looks like, then I could use the 【Analysis Glasses】 to analyze relevant information... Forget it, there's a way when you get to the mountain, let's take it one step at a time!"

He put the book in his hand back on the bookshelf and continued to view other books.

Subsequently, he found another note record, which read:

More than four hundred years ago, during the Warring States Period, there was a swordsman who drove Muzan Kibutsuji into desperation, named: Yoriichi Tsugikuni.

Yoriichi Tsugikuni, the second son of the Tsugikuni family during the Warring States Period. He had a twin brother, Michikatsu Tsugikuni. Yoriichi Tsugikuni was the creator and user of the Origin Breathing · Sun Breathing.

He was born able to use Breathing Technique and the "Transparent World," with extremely high swordsmanship talent and attainments, and was called by his brother a person who was "favored by the gods."

He was the first swordsman to awaken a Demon Slayer Mark, possessing the mark from birth, and caused other swordsmen around him, including his brother Michikatsu Tsugikuni, to awaken the mark.

Also because of his special constitution, he became the only swordsman in more than four hundred years who opened the mark and lived past the age of 25, even living to over 80 years old.

Sun Breathing has huge lethality against demons, which made Yoriichi Tsugikuni the only swordsman capable of driving Muzan Kibutsuji into desperation...

Seeing this, Zero's brow furrowed slightly. The book mentioned 【Breathing Technique】, 【Demon Slayer Mark】, and 【Transparent World】. He already knew what Breathing Technique was.

He had fought with several Pillars before, and his analysis glasses had analyzed the Breathing Technique they used, which was a breathing method that could strengthen cardiopulmonary function and allow the blood to obtain a large amount of oxygen in a short time, which could significantly improve human physical ability, allowing people to temporarily have physical strength equivalent to evil demons, and fight against evil demons...

But he didn't quite understand what 【Demon Slayer Mark】 and 【Transparent World】 were.

"Let's try it, I hope I can know what it's all about."

He turned on the projection screen mode of the "Analysis Glasses." Immediately, a 3D holographic virtual screen one meter long and half a meter wide appeared in front of Zero, and he entered a command.

【Search: Demon Slayer Mark.】

【Searching... Search successful!】

"As expected, it works. Let me see what this so-called 【Demon Slayer Mark】 is?"

【Demon Slayer Mark: After the Demon Slayer Mark is opened, it can significantly improve physical fitness! Anyone who appears with a Demon Slayer Mark will cause people around them to open the Demon Slayer Mark one after another, like resonance.

When opening the Demon Slayer Mark, the body temperature needs to reach 39 degrees, and the heart rate needs to be over 200 beats, so it will cause a great burden on the body.

Note: Congenital Demon Slayer Mark openers are very different from acquired Demon Slayer Mark openers; acquired Demon Slayer Mark possessors all live no longer than 25 years old!】

"So that's it, but the conditions for opening this 'Demon Slayer Mark' are actually like this. Why does it always feel a bit like 【Overload Operation】? If a machine is overloaded, it will increase the operating power, but it will also appear in a high-temperature situation, and it will also shorten the service life... Wait, shorten the service life?!"

Zero seemed to have thought of something. The notes recorded that Yoriichi Tsugikuni was the only swordsman who opened the mark and lived past 25 years old, even reaching over 80 years old.

And the analysis glasses mentioned that anyone who opened the mark lived no longer than 25 years old. In other words, if the mark is compared to a machine's overload operation, doesn't that indirectly mean directly shortening one's future life to improve combat effectiveness?!

"The notes mentioned that Yoriichi Tsugikuni had a special constitution, while my analysis glasses obtained the result of congenital and acquired. Presumably, Yoriichi Tsugikuni was a congenital special constitution, so opening the mark was equivalent to having no side effects, while the acquired mark had side effects..."

Thinking of this, Zero took out a notebook and pen from his nano-space and recorded all this down.

After recording, he continued to search for relevant information.

"Just now the notes also mentioned Yoriichi Tsugikuni's brother Michikatsu Tsugikuni, and his brother said that Yoriichi Tsugikuni was favored by the gods... but why are there no records about his brother Michikatsu Tsugikuni? Sigh, forget it, continue to view the notes, maybe there will be some later..."

"Wait... Yoriichi Tsugikuni? Michikatsu Tsugikuni? Demon Slayer Mark?" Zero seemed to have thought of something.

The notes mentioned that Yoriichi Tsugikuni was the only swordsman who lived past 25 years old, but didn't mention a second swordsman with a mark who lived past 25 years old.

Zero drew a triangle in his notebook, wrote the name of Yoriichi Tsugikuni in the upper left corner, wrote the name of Michikatsu Tsugikuni in the upper right corner, and drew a circle in the middle of the triangle with the words 【Demon Slayer Mark】 written on it, but stopped at the bottom corner...

Looking at this composition, Zero had been thinking about a problem. There seemed to be some connection between the two, or perhaps there was the intervention of a third party?!

If it was the intervention of a third party, who would it be?

Thinking about it, a name suddenly appeared in his mind: Muzan Kibutsuji!

And according to the collected information, Muzan Kibutsuji was a demon who had lived for thousands of years. If the third-party intervener was this Muzan Kibutsuji, it was not impossible.

For example, one day during the Warring States Period, Muzan met Michikatsu Tsugikuni and saw that Michikatsu Tsugikuni was worried because he couldn't live past 25 years old due to opening the mark, but Muzan Kibutsuji needed powerful subordinates and wanted to take him in as a demon to be his subordinate.

And the condition he offered to Michikatsu Tsugikuni was: he could let him live longer and even become stronger?!

This idea, in Zero's hypothesis, although somewhat fantastical, was not impossible.

So he wrote the name of Muzan Kibutsuji in the bottom corner.

Zero made two bold assumptions in his mind:

First: Michikatsu Tsugikuni couldn't live past 25 years old because of opening the mark, and later fought Muzan Kibutsuji because he met him, and finally died in battle!

Second: Michikatsu Tsugikuni agreed to Muzan Kibutsuji's request and finally became a demon! And an extremely powerful evil demon!

These two ideas, no matter which one, were not necessarily unfeasible, but Zero was more inclined to the second one!

As for why, he also made a guess: The Tsugikuni family was a very powerful family during the Warring States Period. Because of Yoriichi Tsugikuni's unparalleled talent, he was valued by the family, which made his brother Michikatsu Tsugikuni feel jealous.

Zero assumed he was Yoriichi Tsugikuni and thought about the problem from Yoriichi Tsugikuni's perspective: Yoriichi Tsugikuni was a person who valued feelings very much no matter what happened, and he also respected his brother very much. He would share everything he had with his brother...

And then he assumed he was Michikatsu Tsugikuni and thought about the problem from Michikatsu Tsugikuni's perspective: Michikatsu Tsugikuni saw that Yoriichi Tsugikuni showed unparalleled talent and was valued, which made him gradually jealous in his heart. In Michikatsu Tsugikuni's eyes, everything Yoriichi Tsugikuni did for him was hypocritical... ===== CHAPTER 10 =====