Watch her out, okay?

While Isao decided to rest for a while, Muzan, who had almost died, was very frightened and trembling, like a newborn fawn. At the same time, his heart was in fury, as it had been a while since he had received such a humiliation from someone. 

Even so, he endured it alone, and he didn't show this disgraceful state of himself to anyone except for Biwa Demon, who was in control of the Infinity City. However, soon, Biwa Demon would probably remember nothing as he would modify her memory so she wouldn't remember his disgraceful state. 

Muzan might have been able to control all the demons under him, and their lives were as good as in his hands, but even so, he had never let them loose or shown his weakness in front of them.

He ruled all of them with terror, and if they lost that terror, then they would fight him. 

Moreover, there was also an exception who could escape his rule and curse. 

This demon escaped from him, and she lived quietly, yet when there was a chance, he was sure that she would bite him like a viper, injecting all of her venom into her body so he would disappear from this world. 

Still, if his opponent was only this demon and the Demon Slayer Corps, he didn't care much, but Isao was different. 

This young man—the one he had ignored, someone he thought was a bug that he could trample anytime—was pretending to be prey, appearing weak so he would let his guard down before he devoured him. 

"Those cursed Demon Slayers... Kagayashiki... how long are you going to block me to achieve my dream!" 

Muzan wasn't sure how Kagaya was able to find Isao, but for one thing, he knew that Isao was an existence that was similar to Yoriichi Tsugikuni. 

"Unfortunately, he is a human." 

This was their weakness, their sin, and the reason why they couldn't defeat him. 

Humans had a limited age, and sooner or later, they would die. 

Isao, who had awoken the "Demon Slayer Mark," also should have died faster than most, so Muzan knew that everything would be alright. 

Yet, even so, Muzan couldn't erase the uneasy feeling in his heart. Nevertheless, it wouldn't stop his hatred toward Isao, Kagaya, and the Demon Slayer Corps. He was going to destroy all of them, turning them into his food, eating their flesh, and telling them the price for antagonizing him. 

"Wait... soon, I will return and kill all of you!" 

Muzan was patient and wasn't in a hurry. More importantly, he had to heal his body. At the same time, his desire to grow stronger and stand under the bright sun also became stronger. 

"I will be the last one to laugh. I will be the winner." 

Muzan kept muttering as he closed his eyes to recuperate and regenerate the body parts that he had lost. 

A millennium had passed and he was the one who had outlasted all of them, and this wouldn't change no matter what. 

At the same time, Muzan wished to bring the greatest despair to Isao, but unfortunately, he knew nothing about Isao. 

Whether it was Isao's name, position, or anything else, Muzan was clueless. 

'However, I will find your importance soon.' 

When he found out everything, he would give Isao the greatest despair! 

Still, before that, Muzan thought of a boy whom he had almost killed yet saved by Isao. 

'I'm going to kill him first.' 

Isao aside, Muzan felt it was easier to kill that descendant of "Sun Breathing." 

Somehow, he felt better, and soon, he fell into a deep sleep. 

Yet, while Muzan was resting so he could become better sooner, Tanjiro went to talk with his mother and little sister about his plan to become the Demon Slayer. 

"Mom, I will become the Demon Slayer. By the way, do you know the dance Dad showed us and taught me? It seemed to be the origin of the breathing style, the "Sun Breathing"! It is the strongest breathing style! Ah, the breathing style is the technique used by the Demon Slayer to hunt down a demon! Oh, right, the income from the Demon Slayer is also huge! I will also get a lot of money for all of us!" 

Still, Tanjiro also understood that being a Demon Slayer was a dangerous profession, and he might even lose his life anytime, but even so, he didn't want to make his mother worried. He had to tell her that he would be okay and told her not to worry. 

"The one who will teach me is also a strong Demon Slayer, too!" 

As Tanjiro kept talking, Kie Kamado, Tanjiro's mother, could only shed tears silently. She wished to stop her son, but she knew that she couldn't. After she came to the Butterly Manor to take care of her wounds and also her daughter, who had become a demon, she knew that there was no other choice for her son to become a Demon Slayer. It was impossible for them to return to their normal life, especially when a demon might target them again, and this was the only way for them to find a clue to cure Nezuko. 

Watching Nezuko, her only daughter, who was the only one who stayed alive from that disaster, Kie felt her heart was in pain. It was so painful that she cried, especially when their painful and dead bodies kept reappearing in her dream, but she knew that she couldn't cry, especially when she would send Tanjiro, who was ready to bet his life to fight a demon. 

Her son was about to embark on a dangerous path, and he might die, but he tried to tell her that everything would be okay. 

If only she could do something... unfortunately, she couldn't. She was just a weak woman who could do nothing except rely on her only son. 

"Tanjiro..." 

Kei took a deep breath, trying not to choke or cry. "Mom can't stop you, but promise us that you will be fine. We are waiting for you here." Following her son to become a Demon Slayer wasn't possible; the only way for her and her daughter to have a stable life was to stay in the Butterly Manor. 

No, to be exact, to follow Isao. 

If there was a reason why Nezuko wouldn't be killed and could be let go like this, it was all because of Isao. 

As the strongest Demon Slayer, Isao's words had a lot of weight, and as long as he was there, nothing would happen to anyone. 

This was the confidence that everyone had, especially toward the young man who almost slain the Demon King, Muzan Kibutsuji. 

Even if Nezuko was around and stayed inside the Butterly Manor, the place where everyone was hurt, no one thought that something would happen to them, especially when they had seen how Isao treated Nezuko like a pet. 

Watching her (his) daughter (little sister), Nezuko, who sat obediently with a bamboo muzzle on her mouth, used to hold her urge to bite. When they saw her like this, it was impossible to think of her as a demon, but it was also hard for them to think of her as a normal human. 

Whether it was Tanjiro or Kie, they knew that if there was someone who could save Nezuko, it would be Isao, especially when they knew what kind of powerful man Isao was. 

Not only Isao's mind but also wealth, power, and everything else. 

At the same time, Tanjiro also felt regret for making such a hasty decision to move and interrupted Isao's battle. If he just stayed in silence obediently, then it wouldn't be hard for him to ask Isao to help Nezuko. Yet, all of this had happened, and it was impossible for him to ask Isao such a shameless request. Moreover, there was nothing he could offer to Isao. 

Well, there was one, but Tanjiro knew that Isao had a wife, and Isao was about to become a father.

With all of that, it was definitely impossible for Isao to show an interest in his little sister. 

If Isao knew what Tanjiro was thinking, he would also agree since he really didn't have an interest in Tanjiro's little sister, Nezuko. 

Still, when Kie saw her son in silence, she somehow understood what Tanjiro was thinking. However, unlike her son, who was still naive about the world, she understood many things. Nevertheless, it was impossible for her to tell what she planned to do. 

Well, it wasn't like her plan could be successful, but she really couldn't think of a way to solve all the problems of their family except for this method, and she was sure that her husband in heaven would forgive her for this. 

"I will." Tanjiro nodded and made a promise to his family that he would be okay since he knew that he was the only one that they could rely on. However, before he left for training under the Wind Hashira, Sanemi Shinazugawa hoped to meet Isao, hoping that Isao could take care of his family. 

Unfortunately, Isao was nowhere to be seen on the Butterfly Manor, leaving for Tokyo. 

"...Is-Is that okay?" 

While Tanjiro was speechless, Isao had left his little sister in the place where many people were wounded without even thinking about bringing her with him.

This guy was so careless!

Tanjiro wanted to complain, but he couldn't, considering how low his position was. Instead, this made him realize how weak he was and made him wish to get power so he could control his own fate.

'I have to become stronger!' 

That way, he could save his little sister and take care of his family without fully depending on someone. 

"It should be fine." Shinobu nodded and gently smiled. "After all, if your little sister tries to harm anyone, I can kill her, so make sure that nothing will happen, okay?" 

"....." 

Tanjiro decided to remind his mother to watch over Nezuko as much as possible.