Ultimate Being from the Tokonosu City

During his passing out, Isao didn't just rest. Instead, he also sorted out all of the information on all the DNA that he had absorbed, especially the DNA of Kanae Kocho and Doma. 

At the same time, he also discovered a new ability in his system: a simulation. 

The use of this ability was quite simple, and it allowed him to create a simulation in his head of a variety of information that was recorded in his brain and system. 

If he gave an example, he could simulate how he would appear or how different he was when he absorbed the DNA of an animal such as a rat. 

A rat was a disgusting animal, so there was no doubt that if he transformed into one, even if he was handsome, he would be disgusted. However, there was no doubt that a rat also had its own good points, such as environmental adaption, disease immunity, and even climbing.

The simulation ability helped him see how he would appear with the absorbed DNA and select only the good parts of the DNA while discarding all the bad parts. 

Isao could also create a field and character with a variety of combinations that he could control by himself. If he had made an example, it would have been like a virtual reality world within his mind, so using this ability, he had been trying to familiarize himself with all of the abilities, talents, knowledge, and others that he had gained from all the DNAs that he had absorbed. 

Isao also had been using this ability to sort out all of the DNAs within his body, erasing all the bad parts and absorbing the good parts. Still, it didn't mean that the bad parts were bad, and he kept all of them since he could use that data to transfer those bad parts onto others, giving them defects within their bodies. 

Yet, Isao had to say that Doma's DNA greatly enhanced his ability, especially when, as a high-ranking demon, Doma could manipulate his body with ease.

After he gained Doma's DNA, Isao was like a fish that had entered a large aquarium. 

Nevertheless, while Doma's DNA was great, especially after he had gained unlimited stamina and endurance, it didn't mean that his DNA was all great since, as a demon, Doma also had several weaknesses. 

Those weaknesses were sunlight, a weapon composed of a special alloy made from Scarlet Crimson Iron Sand and Scarlet Crimson Ore, wisteria, starvation, and the curse of Kibutsuji. 

Among all of those weaknesses, the most troublesome ones were starvation and the curse of Kibutsuji. 

The curse of Kibutsuji came after one became a demon. Frankly, being a demon wasn't all that great since their progenitor, Muzan, was a coward and cautious man. The blood that was given by Muzan contained a curse that was created by Muzan, so if any demons divulged his information or betrayed him, they would die immediately as the curse within their bodies would run amok, causing the regeneration of their bodies to cease to exist and cells belonging to Muzan inside the demon would kill them. 

Moreover, this curse could also locate them, reading their minds and peeking at the memories of the demon. 

It might not be wrong to say the moment one became a demon, their lives were in the hands of Muzan. 

So, the moment Isao got Doma's DNA, he erased this weakness immediately since it would have been troublesome if he had been tracked by Muzan. Still, compared to the curse of Kibutsuji, starvation was an even more troublesome weakness for him to handle. 

With his ability, Isao could erase the curse of Kibutsuji with ease, but for starvation, he needed a long time to modify it since it was related to the unlimited stamina and endurance of the demon. 

Yes, the demon might have unlimited stamina and endurance, but it needed to eat a human's flesh, or else it would be starvation and might even die if it didn't eat.

In the end, a demon is similar to a human since it needs to eat to bring unlimited stamina and endurance to its body. However, even if they didn't eat, it didn't matter since they could consume their living force or vitality, which was almost unlimited. 

Yet, with this knowledge, Isao knew that there was no such thing as unlimited stamina and endurance. When one wanted something, one had to pay for something. If one wanted their bodies to move all the time, they had to eat. Even if a demon was a supernatural being that had escaped the realm of common sense, it still couldn't escape from the law of conversation energy. 

However, this didn't mean that he had to eat human flesh since, with his ability, he changed the need to eat human flesh into eating small amounts of food to give him nearly unlimited stamina and endurance.

By absorbing Doma's DNA into his body, he changed everything within his body, transforming it into the best, almost perfect life form. This made him capable of efficiently turning a small amount of energy into a significant amount of stamina and endurance. 

Besides that, he could also drain his almost immortal life force in exchange for supporting his stamina and endurance, but it might be better to eat since it would be weird if he didn't eat anything, right? 

At the same time, Isao thought that the word unlimited might be a little exaggerated, but it wouldn't be wrong to say that his stamina and endurance had reached a supernatural level with nearly an unlimited level.

Frankly, there was no doubt that compared to everything, including all the abilities, knowledge, talents, etc., which he gained from Doma's DNA, supernatural stamina and endurance were his greatest rewards. 

At the same time, his desire to devour Muzan was even greater, especially when he knew about the curse of the Kibutsuji. 

Yes, this curse might be dangerous, but it was also the sweetest fruit for him since as long as he devoured Muzan, he gained all the abilities, talents, knowledge, and everything of all the demons that Muzan had ever created. 

The curse of Kibutsuji was a connection between Muzan and all the demons. 

If he got Muzan, it meant he would get all the demons. 

During his sleep, he was thinking of activating the curse of Kibutsuji to track Muzan, but he knew that it was impossible since while Muzan could track all the demons below him, it was impossible for the demon below to track Muzan. 

Muzan was too careful and cautious, so it was impossible for Muzan to leave a weakness or something that could lead him into a dangerous situation. 

As for letting Muzan track him with the curse of Kibutsuji, so Muzan would appear before him? 

Isao was afraid that instead of appearing before him, Muzan would activate the curse of Kibutsuji to kill him directly. If this curse failed to activate, Muzan would hide like a turtle inside its shell, and he wouldn't come out no matter what. Even worse, there was also a demon with the ability to create another space to hide, which made it even more impossible for him to track him. 

So, the only way for him to meet Muzan was by luck. 

Yet, with his luck, could he meet Muzan?

So, his next plan was obvious: replicate the luck of the protagonist of this world, Kamado Tanjiro. 

Still, as long as Isao was able to meet Muzan, he knew that Muzan couldn't escape from him. 

However, Isao wasn't in a hurry, and it was a rare chance for him to return to the Taisho Period. He thought of taking a little trip around the world, watching the novelty of the world of the past. Moreover, there were also many breathing styles, and he thought of learning all of them or even creating a new, better one than the Sun Breathing Style, the origin of all Breathing Styles. 

After everything had been decided, Isao opened his eyes slowly, recovering his eyesight as he saw an unfamiliar ceiling. He also saw many other things, such as the wooden ceiling, a futon that was too short for his body, and, at the same time, the presence of several people who had been taking care of him after he had passed out. 

Still, if there was something that caught his attention the most, it was how Kanae, who was wounded, sat by his side and checked on his condition attentively, even if she was told by many to rest. 

Yet, the moment he opened his eyes, he naturally attracted Kanae's attention, who looked at him with a surprised and happy expression, and soon, he also attracted everyone within the room.

"You have woken up!" 

At that moment, everyone was excited.