Ultimate Being from the Tokonosu City

Under normal situations, all the humans that had turned into demons had to be killed. 

Why so? 

It was because after they became demons, they wouldn't be able to live without the blood or flesh of a human. They had to rely on human blood and flesh to live, and if they didn't do so, they would die. 

All the people in this world were like that; even one of the Hashira, the Wind Hashira, Sanemi Shinazugawa, had to kill his mother, who had become a demon, to protect his siblings. 

Yet, as the protagonist, Tanjiro has always been different. Even though there shouldn't be any chance for a demon to return as a human, Tanjiro's little sister, Nezuko Kamado, was able to fight alongside her older brother as a demon, breaking away from Muzan's control, living under the sun, and also becoming a human once again. 

Something impossible became possible; this was why Tanjiro was the protagonist, and the others weren't. They could only die, becoming nutrients, so Tanjiro could become stronger as the protagonist. 

Still, compared to Takeshi Komuro, Tanjiro was a good guy since he wished to save his family, ignoring the shame and begging all of his might. 

"Iinuma-sama, I beg you! I will give my family a secret technique! My body! Everything! Even my life! Please, I beg you not to kill my little sister, Nezuko! She is just sick! I-I am sure that she will be fine after this! She will definitely be fine! She won't hurt others! I beg of you! I beg you!" 

Tanjiro kept repeating those words as he smashed his head on the dirty ground several times, kowtowing, begging desperately, continuously, even if his head was all bloody, so he could save his family. 

Still, Isao didn't answer Tanjiro and looked at Shinobu, who was troubled. "What's wrong?" 

"It's like this..." 

As Tanjiro kept kowtowing toward Isao while hugging his little sister, who had turned into a demon, Shinobu told Isao about what was happening when he rested. 

When Isao told her to check on the victims, Shinobu went to check on Tanjiro and his family without hesitation so she could help Isao faster. Still, Tanjiro was fine and all as he was saved by Isao, the plot armor, and as a protagonist, it was impossible for him to die. However, Tanjiro's family was different, as the majority of them had died. 

Only Tanjiro's mother and little sister were alive, but unlike his mother, the little sister had become a demon. 

With the transformation of Nezuko into a demon, naturally, everyone thought to take down this monster. While it was a cruel decision, there was nothing they could do since, sooner or later, Nezuko's existence would become harmful to society. 

Those who became Demon Slayers mostly had an experience with the demon before they became a Demon Slayer. Whether their families were killed or their families had become demons, no matter what, they knew that there was no possibility of saving Nezuko and killing her was the best act since if they left her alive, then she might attack the innocent, eating them due to her needs. 

Yet, how could Tanjiro accept that? 

Nezuko was his little sister, and he also didn't understand much about a demon, so watching his little sister, who was growling like a beast, while he was frightened, he thought that she was just sick and as long as she was cured, then it was all fine. 

Yet, was there even a cure for one to become a human after one became a demon? 

If it happened to someone else, it would be impossible, and nothing could save them anymore, but it happened to Tanjiro's little sister, Nezuko Kamado, so everything was possible. 

Still, while the others were cornered about Nezuko, who became a demon, Shinobu's focus was on something different. If there was a demon that could transform another into a demon, then there was only one. 

"Isao... was that the demon that you fought before?" Shinobu might not have noticed, but her voice was trembling. 

"Muzan." 

"...." 

Shinobu's eyes widened, and she fell into shock. Then, she quickly thought about what was happening before focusing on Tanjiro. 

While Tanjiro didn't understand, he knew that his situation had worsened due to Shinobu's expression. 

"Yo-You shitty bastard!" 

Her roar startled everyone, and they wondered what was happening, but as the conversation between Isao and Shinobu wasn't that loud, they knew nothing. 

As for Kanroji, who was a little silly, she didn't understand their conversation even if she heard them. 

However, Shinobu, who understood everything, was so enraged!

"You...! You...! You...!" 

Shinobu felt like her emotions were like a broken dam, and it was impossible to hold all the horrible and negative feelings inside her heart. 

Muzan Kibutsuji. 

This was the enemy they had vowed to kill no matter what and the cause of every terror caused by a demon. 

This guy was a monster, something that should be erased from this world, and this was the wish of every Demon Slayer from the millenniums until now. 

Everyone had been working hard for that wish; many died and sacrificed, but they never stopped with their battle and continuously fought, whether it was to protect or to kill those dammable demons. 

Then, dawn came on the darkest night. 

No, it should have been a good day for the demon, which ended when Isao came, and everything became dark for them. 

Yet, at the critical moment, when Isao was about to end this nightmare completely, Tanjiro suddenly came and interrupted Isao's battle, giving Muzan the chance to run away and, once again, erasing their chance to erase this nightmare. 

Knowing all of that, how could Shinobu stay rational? 

How could she stay calm? 

Yet she was also helpless since if she were asked whether she should save someone or kill Muzan, what would she do? 

Still, fortunately, Shinobu was the first to hear this news, but if it had been Kagaya, he might have already chopped Tanjiro's head! 

Still, Shinobu's anger made everyone confused, and Tanjiro, who was in fear, could only lie in fear as he was surrounded by many men, holding their weapons while ready to kill his little sister anytime. 

Tanjiro only wanted to protect his little sister and his mother, who were still alive, and he knew that the only one who could protect his family was Isao, the one who led all of them. 

However, Isao didn't pay attention to him and seemed to be in deep thought. "How is his mother?" 

"She is fine and still passes out now..." 

While Shinobu was helpless, there was nothing that she could do, especially when Muzan had run away. Still, it couldn't stop her from cursing Muzan, who was such a cowardly bastard!

"How about you? Are you okay?" 

Shinobu looked at Isao worriedly while checking his wounds. 

"I am fine." 

Kanroji's strong and soft body supported him well. 

Still, Isao felt a little weak, so he decided to lean on Kanroji's soft body for a little longer.

However, when Isao's eyes met Tanjiro again, he started begging again like a broken radio. 

"Iinuma-sama, I beg you! I beg of you! Please! I will do anything! I will give my family a secret technique, everything! So can you please—

Slap!

Tanjiro quickly shut up when Isao slapped his cheek. 

"Tanjiro, listen to me. Your sister has become a demon." 

"De-Demon?"

"You still remember the story that was told by that old man at the foot of the mountain, right? A demon exists, and it haunts all of us until now. All of us here are part of an organization that fights and protects everyone from the demon."

'Then, my family secret's technique...' 

Instantly, Tanjiro understood why Isao wished to get his hand on his family's secret technique, and at the same time, an endless regret overflowed onto him. 

If only he hadn't become so persistent... if he had just taught Isao... if he hadn't been so greedy, would all of this have happened? 

If Tanjiro had just agreed to teach Isao and brought Isao and his group back to his home, then would all of this tragedy happen? 

Tanjiro lamented at how stupid he was. 

"But... why no one told me this...?" 

If Tanjiro knew about the demons and knew that his family's secret technique was used to protect everyone from the demons, would all of this happen? 

"We and the government keep this matter a secret since if everyone knows, it will cause panic for everyone. If everyone is panicking, then what do you think will happen, especially when the world war has just ended, and there might be another war in the future." 

"....." Tanjiro. 

"....." Everyone. 

"H-Huh? Will there be another war?" Kanroji was dumbfounded. 

"Probably, but that's the concern of the world, and our concern is with the demon, so let's put that matter aside now." Isao then looked at Nezuko and said, "As I have said before, your little sister has become a demon, and sooner or later, she will hunt an innocent, so we have to kill her." 

"N-No! She won't do something like that! She won't hunt an innocent! She is a good girl!" 

"It's not a matter of her personality. It is her need to hunt down a human. Like how a human eats food every day, the demon has to eat a human if they want to stay alive." 

"N-No way..." Tanjiro's face turned pale, and all the blood drained from his face. He didn't want to believe it, but he knew that Isao didn't lie, or rather, there was no need to lie to him since there was no value in him. 

Watching how strong Isao was, Tanjiro felt intense shame, thinking how Isao might profit from his family's secret technique that wasn't much different from just a mere dance. 

If Tanjiro was a wealthy man, it might be different, but he was a poor boy who cared for his widowed mother and many of his little siblings. 

What kind of value could be gained from deceiving him?

Tanjiro wasn't stupid.

Yet, because he wasn't stupid, he didn't know what to do since he knew that his little sister, Nezuko, would kill people sooner or later for her needs.

Like how a human would get hungry and eat food, she would be the same, but unlike a human, who ate rice, vegetables, and meat, she would eat human flesh!

If so, then could he stop her? 

Tanjiro didn't want them to kill Nezuko, but he also couldn't bear to see his little sister eat the innocent. 

Slap.

Once again, Tanjiro was slapped, making in a daze. 

"Wake up." Isao looked at Tanjiro and asked, "Are you going to give up?" 

"I-I won't! I will stop her! I won't let her eat innocent food! If she eats someone, then I will kill her and kill myself! I swear to everyone in this place! So, please let her go! I will do everything!" 

That slap woke Tanjiro up, and he said those words loudly to show his determination. 

Isao nodded and thought that this was how a protagonist should be. 

"Okay, let's go back. I am going to rest. Take care of the rest." 

"...." Everyone.

"Huh? Would that be fine? Are you going to let his little sister go?" Shinobu quickly asked. 

Unlike the others, who couldn't fight his decision, as the little sister of the mother of his children, Shinobu could say whatever she wanted to this bastard! 

"It's fine. His little sister is just a weakling anyway, and with me here, what can she do?" 

Isao patted Nezuko's head gently, and strangely enough, she was quiet and docile. 

[You have acquired Nezuko Kamado's DNA.]

[Do you want to absorb it?]

"Thank you! Thank you! Thank you!" 

Tanjiro cried as he bowed his head so many times. 

Ignoring Tanjiro's thanks, Isao didn't forget about Nezuko, but when it was over, he leaned on Kanroji's soft body once again, pretending to pass out. 

Oh, wait, his face fell on Kanroji's chest, but it didn't matter since it was more comfortable. 

"Isao!" 

Yet, for the others, they went into a panic.