Chapter 10: Zero's Guess

Zero imagined himself as Yoriichi Tsugikuni and Michikatsu Tsugikuni, thinking about the problem from their perspectives.

But a guess is a guess after all; without real evidence, everything is just empty talk.

But he still recorded his guess just now in his notebook. If it were true, it might be of some help to himself or the Demon Slayer Corps later.

"It's a pity... the life of a Demon Slayer Mark swordsman is so short! I don't know if those swordsmen now have opened the Demon Slayer Mark? But I think they probably haven't, after all, the strongest Stone Pillar of the Demon Slayer Corps is already 24 years old. If he really opened the Demon Slayer Mark, he might not be here anymore... probably..."

He then put the notes back on the bookshelf, took out another note, and when he was about to open it to view, he remembered the 【Transparent World】 recorded in the note just now.

"But speaking of which, what is this 【Transparent World】?"

【Search: Transparent World】

【Searching... Search successful】

"Phew~ fortunately, it can be searched. Let me see what this so-called 【Transparent World】 is?"

【Transparent World: A world that can be seen when the brain becomes transparent. It is the "Supreme Realm" that can only be reached after trying one's best and enduring pain.

In this state, by concentrating and closing unnecessary senses, the biological body will look as if it has become transparent.

One's own movement speed, prediction and avoidance of attacks will be significantly improved, the blood flow in the opponent's lungs can be clearly seen, the contraction of one's own muscles can be grasped faster, and according to needs, even fighting spirit can be freely closed. Because perception is accelerated, the enemy's actions will also look slower.】

"Uh... speaking of which, what is the difference between this and X-ray vision? It's like X-ray plus infrared sensing... but it does look quite powerful, for this world..."

"No! If it were just Breathing Technique plus Demon Slayer Mark and Transparent World, Yoriichi Tsugikuni couldn't have driven Muzan Kibutsuji into desperation! There should be something else! For example... weapons?!"

When Zero sparred with the Pillars, he found that their weapons all had differences, and their weapons were all called Nichirin Swords!

Sanemi Shinazugawa's weapon was a Nichirin Sword with a white hilt, a light green blade, and a serrated blade pattern, engraved with the four characters "Destroy Evil Demons." The guard was black and octagonal.

Obanai Iguro's Nichirin Sword weapon was a curved serpentine double-edged blade, the blade was purple, and a snake pattern was carved inside the circular guard.

Then, according to this inference, the weapon used by Yoriichi Tsugikuni must also have had a very different, yet similar, effect!

Organizing his thoughts, he put the note book back in its original place and took out the previous note to continue viewing.

But he didn't find relevant information, but found another piece of information from it.

According to records, Yoriichi Tsugikuni once met Muzan Kibutsuji on a certain night and fought with him. Muzan Kibutsuji couldn't beat him and fled, and there was a female demon following Muzan, but Yoriichi Tsugikuni didn't kill her, but let her leave.

Just as the Demon Slayer Corps members arrived, they only found a large amount of blood at the scene and the fleeing female demon, and scolded Yoriichi Tsugikuni for why he did this...

Because of Muzan Kibutsuji's escape, coupled with the female demon he let go, Yoriichi Tsugikuni was scolded by the members of the Demon Slayer Corps, and later expelled from the Demon Slayer Corps...

The record is not very complete, and even somewhat incomplete! But Zero felt that the female demon Yoriichi Tsugikuni let go in the record definitely had something different, or had something different.

In his notebook, he drew another line next to Yoriichi Tsugikuni's name and wrote the words 【The Female Demon Let Go】.

"I don't know who this female demon let go is? If she lived to the present, what identity is she living as? Why did Muzan Kibutsuji let her stay by his side? Or what can this female demon do for Muzan Kibutsuji?"

Zero was somewhat puzzled, and didn't understand why the Demon Slayer Corps at that time would do such a stupid thing?! Expelling Yoriichi Tsugikuni directly without even asking the reason?

And Zero found that it was Yoriichi Tsugikuni who taught his Breathing Technique to the Demon Slayer Corps, which allowed their strength to go to the next level, and they were not so pathetic when dealing with evil demons!

Although they couldn't master Sun Breathing like Yoriichi Tsugikuni, Yoriichi Tsugikuni guided them to modify it based on Sun Breathing, thus deriving other Breathing Techniques.

It can be said that Yoriichi Tsugikuni made an indelible contribution!

"Truly, creation makes fools of people!"

Afterward, he flipped through other notes, but didn't find anything about Yoriichi Tsugikuni's weapon.

"It seems I can't find it... No, it's not that I can't find it!"

Remembering the two Lower Moon demons he encountered earlier, and a piece of information provided by the analysis glasses before fighting them: The thermal effect produced by the Dark Alloy Type Four with energy crystals also has the effect of a Nichirin Sword!

"Heat? When the heat is too high, it will produce burning, just like a piece of high-purity iron encountering the continuous burning of flames will become red-hot, emitting flames..."

"Nichirin Sword? Since my Dark Alloy Type Four with energy crystals will have the same effect as a Nichirin Sword, is the Nichirin Sword also made of special things?"

【Search: Nichirin Sword】

【Searching... Search successful】

【Nichirin Sword: The blade is made of sun-absorbing Jade Steel and materials "Scarlet Sand Iron" and "Scarlet Ore." It is the only weapon that can cause damage to demons, and it will show different colors according to the user's attributes.】

"So that's it. No wonder I saw that the weapons of the Demon Slayer Corps Pillars are all different colors! And the material of the Nichirin Sword is made by absorbing sunlight!

It should be that it has been exposed to the sun for a long time in a place closest to the sun to be like this, but it must be more than that. If I'm not mistaken, the location of this Jade Steel should also have volcanoes and the like nearby!"

"But unlike my Dark Alloy Type Four, my Dark Alloy Type Four was manufactured by me several times using highly precise instruments, and the dark alloy was also specially modified!"

Subsequently, Zero took out two energy crystals to check. One energy crystal was bright red and brilliant, and the other was transparent and snow-white.

They were converted from the heat and ice energy generated near the solar system and near Pluto.

They were absorbed and compressed by special high-precision instruments, and then forged into crystals using special meteor iron to inject energy.

The crystal after injecting solar energy would become bright red. Because the energy was too huge, it could continuously provide energy for the battle armor and weapons to fight with alien beasts in the void.

And the ice energy generated by injecting Pluto could produce a freezing effect, basically used for battle armor heat dissipation and freezing the movement ability of alien beasts.

After watching for a while, he put the energy crystals back into the nano-space.

"But from this, it can be inferred that the weapon used by Yoriichi Tsugikuni should be made of the purest Jade Steel, right? If my guess is correct, the weapon used by Yoriichi Tsugikuni should be black or red... or both?"

Subsequently, he drew another line next to Yoriichi Tsugikuni's name in his notebook and wrote the three words 【Nichirin Sword】.

"The heat generated by adding energy crystals to Type One and Type Two in my Dark Alloy Type Four can suppress the regeneration of evil demons, so it should be that the cells are destroyed by the heat, and that's why it's like this, plus decapitation will turn into ashes!"

"……But is it really that easy? What if a demon appears that cannot die even if decapitated, then what should be done? For example: Muzan Kibutsuji! After all, Muzan Kibutsuji has lived for thousands of years and must have many ways to save his life. Perhaps overcoming decapitation might be one of them?!"

He drew a line under the name of Muzan Kibutsuji in his notebook and wrote the four words 【Overcoming Decapitation】, then added a question mark.

But looking at the female demon Yoriichi Tsugikuni let go in his notebook, he drew another line connecting to the name of Muzan Kibutsuji.

"What is the relationship between this female demon and Muzan? It's definitely not as simple as a superior-subordinate relationship! Then there is only one possibility: enemies!"

"This female demon should master something, so Muzan kept her by his side! What exactly is it? No, no... it should be that this female demon has some identity that can help Muzan Kibutsuji!"

Thinking about it, Zero still couldn't figure out the answer. Just as he was about to give up, a flash of inspiration suddenly flashed in his mind.

Remembering a sentence recorded in the note just now: Yoriichi Tsugikuni once met Muzan Kibutsuji on a certain night...

"Evil demons can only act at night, so Muzan should be looking for a way to restrain sunlight, and that female demon should be proficient in medicine, so Muzan turned her into a demon and kept her by his side! Then according to this inference, the identity of that female demon should be a doctor proficient in pharmacology! It's just that she happened to meet Yoriichi Tsugikuni during the action..."

Thinking clearly about the reason, he drew a line under 【The Female Demon Let Go】 and wrote the word doctor.

Although this was all Zero's guess, he felt vaguely in his heart that it wasn't that simple!

"Although the identity of the female demon let go is only my guess, I always feel that it is not wrong in the dark... It seems that when I have time later, I will look for some information from the doctor's side, especially doctors who only practice medicine at night! I hope to find that female demon through this."

Subsequently, he drew another line next to Muzan Kibutsuji's name and wrote 【Creature Not Afraid of Sunlight】, then added a question mark.

"Becoming an ultimate creature not afraid of sunlight... I remember Xiao Yue once checked some information before, which recorded a plant called 【Blue Bianhua】. Muzan Kibutsuji seems to have been looking for this kind of thing all along..."

【Search: Blue Bianhua】

【Searching... Search successful】

【Blue Bianhua: A plant that only blooms during the day and has only two or three days of blooming time in a year.】

"Pfft~" Seeing this information, Zero suddenly felt it was very funny, and also felt worried about the IQ of that idiot Muzan Kibutsuji.

The Blue Bianhua that Muzan Kibutsuji had been looking for for thousands of years only blooms during the day and can only survive for two or three days a year.

One can imagine what kind of expression Muzan would make if he knew the news of this matter?! Just thinking about it makes it feel funny, and the Blue Bianhua only has two or three days of blooming time a year, and I don't know when it is!

"That idiot Muzan, his IQ is worrying! No, no, no, I can't laugh..." But as soon as he thought of the funny appearance of Muzan being furious if he knew about this, he really couldn't help it!

Although he didn't know what Muzan Kibutsuji looked like, it didn't prevent Zero from imagining it casually.

It was fortunate that he held back his laughter; otherwise, if Amane Ubuyashiki outside the door heard it, he didn't know what she would think.

Calming his heart, he drew a line under 【Creature Not Afraid of Sunlight】 and wrote 【Blue Bianhua】, but he always felt that something was missing.

He also wrote the words 【Bai Chi, IQ is worrying】 in his notebook, then drew an arrow pointing directly at Muzan Kibutsuji's name.

Muzan, who was hiding in the Infinity Castle, suddenly sneezed, and his body felt a chill.

"Achoo! What's going on? Why do I feel like someone is going to be unfavorable to me?!"

Zero looked at the records in his notebook. Without knowing it, he had already queried some relatively important notes. Although there were not many, they were more than the information he and Xiao Yue had collected some time ago, and even more complete.

Afterward, he began to query information about Breathing Technique, and wrote the words 【Initial Breathing · Sun Breathing】 on another page of his notebook.

"According to the records in the notes just now, the initial breathing is Sun Breathing, but because many people cannot master and bear the power of the sun and cannot learn Sun Breathing, many other schools of Breathing Technique have been derived. I don't know if I can search for relevant information?"

"Let's try it, maybe I can get the information I want from it."

【Search: Sun Breathing】

【Searching... Search successful】

【Sun Breathing: The initial Breathing Technique, the ancestor and foundation of all Breathing Techniques, created and used by the founder of Breathing Technique, Yoriichi Tsugikuni.

Sun Breathing can emit the same energy as the sun, which has huge lethality against demons. At the same time, it can also directly attach energy to the blade, forming a burning crimson blade—the Red Blade.

After piercing into the demon's body, it will destroy the demon's internal organs, making the demon suffer the pain as if the internal organs are being burned by raging flames, and making the demon's body gradually collapse and unable to regenerate.

Sun Breathing makes the vast majority of people unable to bear it because its power is too powerful, so five major schools of basic Breathing Techniques were derived from Sun Breathing, namely: Water, Thunder, Flame, Stone, Wind.

Members of the Demon Slayer Corps also created a variety of derived Breathing Techniques based on these five basic Breathing Techniques.】

"So that's it. It turns out there are so many types of Breathing Techniques, and these five basic Breathing Techniques should also have branched Breathing Techniques, right? For example, the Serpent Breathing used by Obanai Iguro earlier should also be a branch derived from one of these five basic Breathing Techniques."

He drew five lines around the words 【Initial Breathing · Sun Breathing】 and wrote the names of the five basic Breathing Techniques.

"But what is the 【Red Blade】 mentioned in this information?"

"Red Blade... burning crimson blade? Hmm... the energy mentioned in the information... I think it should be the sunlight absorbed by the Jade Steel, plus the Scarlet Sand Iron and Scarlet Ore, but what is the trigger medium?"

He drew a line next to the words 【Nichirin Sword】 and wrote 【Red Blade】, thinking about the key to it.

"My Type One and Type Two produce heat by adding energy crystals, and the effect is the same as the Red Blade. Then, does the Nichirin Sword also need to add something... No, no, it should be triggered according to something! What exactly is it?"

"Breathing Technique, Demon Slayer Mark, Transparent World, Red Blade... The Nichirin Sword needs to be held by a person to be used, which means... grip strength?! But can people in this world really have such great grip strength? No, no, no, Yoriichi Tsugikuni can, or in other words, Breathing Technique plus opening the Demon Slayer Mark, the strength becomes larger, and it can also be done... probably..."

"Sigh, forget it, wait until I have time to ask Kagaya Ubuyashiki, borrow a Nichirin Sword and try it myself first. If it can be done, then I will teach this method to them, at least let them have more protection in battle..."

Subsequently, he drew a line next to the word 【Red Blade】 and wrote the two words 【Grip Strength】.

Just as he was about to continue querying the information of other notes on the bookshelf, there was a knock on the door.

Knock, knock, knock!

"Lord Zero, it is already night, is there anything you need help with?" Amane Ubuyashiki's voice came from outside the door.

"Uh, I've been here for a day?!" Zero thought to himself, then packed up his notes into his nano-space, turned off the projection of his analysis glasses, put the notes back on the bookshelf, and left the study.

Opening the door, he saw Amane Ubuyashiki sitting at the door, and spoke: "Sorry, Lady Amane, for disturbing you for so long!"

"Oyakata-sama has instructed that if you have any needs, you can tell me, and we will do our best to help you."

"There is indeed one thing. I want to ask if you have a portrait of Yoriichi Tsugikuni from the Warring States Period here? That is, a portrait of the founder of the initial Breathing Technique?"

Zero's idea was very simple. If there was a portrait, then he could use the analysis glasses to analyze the data through the portrait and obtain more information. At that time, perhaps he could know Muzan Kibutsuji's appearance through the information to obtain more useful data.

"Sorry, Lord Zero, I don't know about this, but I can go and ask Oyakata-sama, maybe he knows."

"Okay, then I'll trouble you! I'll come again tomorrow, and I've also found some information that might be helpful to your Demon Slayer Corps."

"Hmm, I will inform Oyakata-sama about this, thank you, Lord Zero!"

"Oh, by the way, if possible, can you help me prepare a Nichirin Sword? A normal one will do. I plan to do an experiment. If my idea is proven correct, then dealing with evil demons might be a little easier."

"Okay, I will inform Oyakata-sama together."

Finally, he said goodbye to Amane Ubuyashiki and left the mansion.

And Amane Ubuyashiki told Kagaya Ubuyashiki about this.

After learning about this, Kagaya Ubuyashiki began to look for Yoriichi Tsugikuni's portrait. If it could help Zero, then it would also be a good thing for the Demon Slayer Corps.

Quiet night.

Zero was on his way to the Butterfly Mansion when he heard Xiao Yue's cry.

"Master!" Xiao Yue flew over directly, landed on Zero's shoulder, and hugged his neck tightly.

"What's wrong, Xiao Yue? Is something uncomfortable?"

"Master, do you not want me anymore?"

"Why do you say that?"

"I haven't seen you all day today, I thought you didn't want me anymore! Wuwu..."

Hearing this, Zero was somewhat dumbfounded. He took Xiao Yue off his shoulder, wiped her tears with his finger, held her in his hand, and comforted her: "Alright, alright, don't cry. I didn't say I didn't want you. I went to the Ubuyashiki mansion today to look for some information, but I didn't notice the time, so I came back late. Sorry, Xiao Yue, for making you worry."

"Really?"

"Of course! Xiao Yue, you are so cute, how could I not want you?"

"Wuwu... that's great, I thought you didn't want me anymore and left me alone!"

"Silly child! I really can't do anything with you. Otherwise, you can go with me tomorrow, so you can rest assured, right?"

"Hmm hmm!"

"It's already a bit late, let's go back to the Butterfly Mansion to rest together!"

"Okay!"

Finally, Xiao Yue stayed directly in Zero's jacket pocket, revealing her head, and returned to the Butterfly Mansion with Zero. ===== CHAPTER 11 =====