Mount Sagiri

Muzan was sitting on a futon, looking out of the broken window. 

A few feet away from him, Ozaki was sleeping on another futon. Last night, she spent hours crying herself to sleep.

Muzan had stayed with her throughout the night. Although he had blocked his ears with his blood demon art and pretended to give her company..

But that was enough for Ozaki; the scared girl felt safe with Muzan around. And could finally go to sleep.

"Yawn~"

Ozaki twisted in her sleep, and opened her eyes with a sleepy yawn. 

She felt she heard a sizzling sound in her sleep, which woke her up.

"Hmmm? Aah!"

Ozaki's confused eyes looked around her room, when she saw Muzan sitting beside her, it made her relax.

But as soon as she saw what he was doing, she exclaimed in shock.

"What are you doing, Mr. Muzan?! Why is your hand burning?"

Ozaki looked terrified. The sizzling sound that woke her up, was the sound of Muzan's flesh buring.

Muzan didn't seem too bothered. He gently turned his head, his blood-red eyes gazed at the shocked girl, before he spoke softly.

"I am training. Demons are weak to the sun."

"I am training myself to resist the sun, by constantly exposing myself to it."

Muzan explained his actions, then kept exposing himself to the morning sun, which was shining in through the window.

Muzan was somewhat used to this painful feeling, but to Ozaki's eyes, this seemed like torture.

"Do demons have such a big weakness? This looks painful."

"Isn't there some other way which can make you resist the sun?"

Ozaki asked Muzan; she didn't like seeing him hurt this badly. There had to be a different way out there that wasn't so painful.

"Another way to gain sunlight resistance?"

"Yes, there is a way. It is very simple too."

Muzan smiled. Then he gestured with his hands.

"There are two siblings who live on top of the mountains, a brother and a sister."

"If I drink their blood, I will become immune to sunlight without any pain."

Muzan smiled widely, his canine teeth were showing fiercely, he was talking about drinking blood, like it was a normal thing to do. 

This scared Ozkai.

"Although-"

Muzan whispered; his wide predatory smile slowly vanished; in its place was a serious look.

He looked at Ozaki with a calm, collected face.

"Although I don't want to do this."

"If possible, I want to develop sunlight immunity on my own, without relying on anyone."

"The power you gain through your own efforts, suits your body the most."

Muzan finished speaking, and Ozaki nodded subconsciously, then blinked her eyes and smiled awkwardly.

"You are great, Mr. Muzan. If I had a choice, I would have chosen the easy way."

"I think, I would have drank their blood. It's inhuman, but it would have been less painful for me."

Ozaki muttered with a shaky voice. She never thought that one day, she would talk about drinking human blood with a demon. What even was her life?

Muzan laughed at her words. 

"I am not a great person. I will still collect the sibling's blood."

"They are my backup plan, in case my training idea doesn't work."

Muzan shrugged; he was not going to ignore Nezuko and Tanjiro. He will still collect their blood and use it in case of an emergency.

Ozaki seemed shocked at Muzan's scummy behavior, but then she smiled.

"Such scummy behavior somehow makes you seem more relatable, Mr. Muzan."

Ozaki felt relaxed; in her mind Muzan was a great man. But it turns out he was human, just like her.

Although human might not be the right word, as he was a demon. But his actions were relatable to her nonetheless.

"Do you have their blood right now? I have an ice box downstairs; we can keep it there."

"I use it to store fresh fish; it should keep human blood fresh as well."

Ozaki offered while tying her hair into a bun. She felt like a murderer after offering this, but she ignored this feeling directly.

Muzan rubbed his chin with thought.

"No, I don't have it. I have asked my subordinates to collect it for me."

"But I am not sure where the siblings live. I only know the general area."

"I hope my subordinates have found their address."

Muzan paused and decided to contact Doma. 

"Be quiet. I am going to contact my subordinate."

Muzan put his finger on Ozaki's lips and closed his eyes to start a telepathic link. It has been a day since he ordered Doma to look for the Kamado family.

Maybe they have a clue by now.

'Doma, did you find the kamado household?'

Muzan spoke to Doma in his mind. As usual, Doma had no emotion inside his soul but still spoke in a cheerful voice.

'Muzan sama! Like you said, we are searching for the Kamado family near Mount Sagiri.'

'But we haven't found them.'

Doma reported while holding a fan to his mouth. Muzan frowned slightly. Doma didn't mind that; he lovingly rubbed a female skull while speaking.

'I have selected two human sisters to do this job, Muzan Sama.'

'They have arrived near Mount Sagiri; they are currently looking around the place.'

'We will find the Kamado family soon!'

Doma finished his report, and Muzan nodded softly. This was the benefit of having human subordinates; they could act freely, even during the day.

'The two sisters are good people, right? If not, chances are Tanjiro Kamado will smell their bad intentions.'

'They might have trouble taking their blood, if he decides to resist.'

Muzan wanted to confirm this point; he didn't want his plans to fail for such a simple reason. 

Doma chuckled, he replied to the query with confidence.

"They are two kind sisters, Muzan Sama. Before you called, I was planning on eating them.'

'But I can wait; I will eat them after their work is done~'

Doma cheerfully sang. Muzan tapped his finger on the floor. If the sisters were kind, then there should be no problem. 

Tanjiro's nose can't detect anything wrong, if the person didn't have evil intentions. 

The plan was going well, Doma had done a fantastic job.

'Good job, Doma.'

Muzan praised his emotionless subordinate, Doma perked up in his seat.

'I am not worthy of your praise, Muzan Sama.'

Muzan chuckled and cut the connection. He sighed in relief at a job well done. Then I looked at Ozaki, sitting beside him.

She was still silent, blinking cutely at him. Muzan couldn't help but smile; human subordinates were really useful. 

And this girl, Ozaki, was a talented human. She was talented enough to become a demon slayer and learn breathing arts in the original story.

Muzan had decided to take her under his command permanently. He could see that she was emotionally injured right now, and was looking for support.

He could act as that support, and become the most important person in her heart.

'When I am done, my status will be the highest in her heart.'

Muzan decided to play this game. Anyway, he had a lot of experience playing family with human women before.

"I checked; my men are looking for them."

"Now leave, I am going to train; if you need anything, you can let me know.'

Muzan smiled gently at Ozaki and looked the other way. The game of family needed patience, and he had plenty of that.