Muzan Kibutsuji x Human Daughter Reader

I

One evening, the little girl (Y/n) was running errands. On her way home, she passed through the tiny, dark alley.

At that point, she encounters a particular man for the first time in her life who will forever change her life.

"Hello mister!" she greeted.

"Hmm? Hello human..You're out late.. Aren't you scared?" he asked.

"No, how about you mister?" she tilted her head. "I'm not scared.. I am the most powerful demon in this world.. Humans are weak"

He wasn't even looking at her, he was simply responding to her. He perceives her as a young child who, after learning that he is a powerful Demon, will either doubt him or be terrified of him.

However, her answer led him to take a closer look at her considering it was so unexpected. (Y/n) gasped as her eyes grew wide.

"You're a demon mister? That's so cool!!" the little girl exclaimed.

"You think so? I'm not surprised.. I look amazing after all.." She agreed with him by nodding. Her unexpected remark piqued his curiosity for the little girl.

(Y/n) waved at him cheerfully knowing it was time for her to go home. "I hope I can see you again mister demon. Take care!" she giggled before walking away.

The man smiles to himself as he observes her leave. "What an adorable little human. Not bad huh" he mumbled.

The following evening, as (Y/n) was strolling, she remembered again the Mister Demon she had met the previous evening. She was startled upon seeing him there once more. Putting a broad smile on her face.

"Hello little human.. Why are you out so late again?" he greeted.  "Hello mister demon we met again!" she smiled.

"You're a strange human aren't you?" he chuckled " I'm glad to see you again.. You don't fear me do you?" he asked in a calm manner.

"You're glad to see me?!" she smiled once more "actually your eyes are beautiful"  she continued and giggled. He looks surprised that a human such as her would say that. "No one ever looked at my eyes They only feared me. Are my eyes really that beautiful?" she nodded cheerfully.

The young girl's compliment truly made him feel pleased but he wants to keep that from coming out as too much. He's not sure why, but this human child certainly drew his attention.

"What's your name?" he asked. "I'm (Y/n). How about you mister?" she replied. "My name is Muzan"

"Hi mister Muzan, I'm glad to see you again" she smiled. "You seem happy to see me again human.."  Muzan lowered himself to match her height and added "Do you want dango?" he offered. "Yes"

"Alright" Muzan stood up of that posture and gestured (Y/N) for her to follow him, which she did. They headed over to the dango store and purchased some for her. They went to the nearby park and sat on a bench there. "Enjoy your dango, little girl" "Thank you"

(Y/N) took a mouthful of it and appreciated it extremely nicely. She looked at Muzan and offered to share it with him, which he refused, however the small girl insisted, so he also took a few bites.

"How old are you?" Muzan asked. "I'm 6 years old" she replied.

Since then, they have started to spend time with each other every night. Muzan treating her dango, they talk to each other, and they enjoy each other's company. With each day that goes by, they learn more about one another. Not until Muzan learned something from (Y/n).

Muzan inquired (Y/N), they were having their usual bonding time. "Why aren't you scared around me despite the fact that I'm a demon? and not just a mere demon, but a Demon King. Why do you love spending time with me so much?" 

It's true, he frequently wondered her behavior toward him. If Muzan had chosen to, he could have instantly turned this little child into a demon or killed her, but he can't. Whether he admits it or not, he simply enjoys being around her. Or, to be more precise, he gradually develops a fondness for her.

"Because you make me smile for the first time. I wish you were my dad instead" she replied. Those words caught him off guard. "What do you mean by that?"  He seems to care about those remarks, judging by the way he speaks. "(Y/n) tell me, is there a problem?" he asked. Then it clicked. (Y/n) started crying out of the blue.

In an effort to comfort the young child, Muzan drew her into an embrace. He simply let her to cry her heart out. He pats her back after saying, "Shhh, it's alright."
She was tense for a long time before finally falling asleep.

(Y/n)'s kimono sleeves were sticking up from her wrist, and her skin around her wrist appeared to be a somewhat purple hue. More sleeves were rolled up by Muzan, who then spotted numerous bruises on her arms.

Muzan took her sleeping form into his arms, she cuddled closer to him, and she snorted. He continued to touch her back while she slept.

He then took her to the infinity castle.

He then carefully treated her bruises without waking her before setting her down on a bed. Then he ordered his demon subordinate a command to look into the events that happened to Y/N.

It appears that her father mistreats her on many levels. He places all the blame on the child since her mother passed away when she gave birth to her.

Due to his own vice addiction, her father likewise spent all of their money on these vices rather than providing for and raising his own child. They were buried with debt on every side.

The people (Y/n) encountered during her life were all cruel to her. She was the target of their wrath since his dad was unable to settle their loan. She was bullied by other children, and adult people criticized her. When she told her father about it, he struck her as usual.

That is why (Y/n) likes Muzan so much since, despite being the Demon King, he is the only person she has ever met who has never treated her badly when they first met. She also had the opportunity to laugh and smile sincerely for the first time in her life because of this.

Muzan became outraged as soon as he heard this. He slaughtered everyone at her father's house, including the peasants who had mistreated her.

"Are you awake my dear?" Muzan called as (Y/n) opened her eyes. "Mister Muzan? Where am I?" she asked. "You're home" he replied. "Home?"

"That's right. Your wish is my command. From this day, I am your father and you are my daughter" he smiled.  "Really?"

He nodded. "You don't have to go through that again. I promise to make you feel safe and loved, my daughter" he said as he pat her head.

She smiled and hugged him. "Thank you. I promise I will be good daughter to you" Muzan just hugged her back and chuckled "You already are"

On that day, the little girl officially became (Y/n) Kibutsuji.