The Shadow's Revenge (Kimetsu No Yaiba X Male Reader)

Prologue

The wind was blowing a steady gust as a six-year-old (Y/N) was outside in the field next to his family house having a mock sword fight with his older brother,

"Nii-san, it's not fair! You have longer arms than me." The small boy whined towards his surrogate older brother, Kuro. The former Divine Heir smiled as he knelt down and ruffled the child's hair.

"Don't worry, (Y/N), one day you will grow up to be big and strong. Then you can beat me, but until then..your Nii-san will always win!" Kuro said with a smile and began to tickle the child, who erupted into laughter.

"Kuro! (Y/N)! Dinner is almost ready!' Akame, the former Divine Child of Rejuvenation called out. (Y/N) ran over and hugged his surrogate older sister with a smile.

"Nee-Chan!" The young boy exclaimed as he began to walk home, while holding both of his sibling's hands.

"Nii-san, Nee-Chan... when are you two going to get married?" (Y/N) asked innocently as both of his older siblings stopped walking and looked at him in shock.

"(Y/N), aren't you a little young to be asking that?" Akame asked, smiling at him.

"Otousan and Okaasan were talking about before we went to bed when you two were star gazing." The boy's response puzzled the two even more.

"How long do you think they knew?" Akame whispered into Kuro's ear.

"I guess a lot longer than we realized." Kuro replied as the siblings resumed their walk back to their house. However, before they could enter, a man dressed in the armor that resembled a samurai ran up to them and got onto his knees holding a girl with blue hair roughly the same age as (Y/N).

"Please, may I see Lord Sekiro and Lady Emma. I beg you it's of utmost importance." The man begged as the siblings looked at one another.

"(Y/N), get Otousan and Okaasan." Kuro ordered. (Y/N) opened the door and ran into the kitchen to see both of his parents about done with dinner.

"Otousan! Okaasan! There's a samurai outside." (Y/N) said as Sekiro got up and grabbed his katana, while Emma picked up (Y/N). As they reached outside, Sekiro removed his hand from his katana and looked at the man.

"Lord Musashi? Why are you here?" Sekiro asked once he recognized the man. Daisuke Musashi was the ruler of the region the family lived in and was a benevolent ruler that treated his subjects justly.

"Please, I have no time left, but my daughter she's in danger and I can no longer look after her. I beg of you to please look after her as if she was one of your own." Lord Musashi begged as he bowed his head down.

"Lord Musashi, please just explain what's going on. I'm sure we can help you out." Emma said. Afterward, Musashi explained how his daughter, Rem, was half-demon as her mother was a demon herself. He then began to explain how he tried to hide her away fearing that other demons would try to take her away or that the Demon Slayer Corps would kill her. After a few tense moments, Sekiro and Emma agreed to take her in. Musashi thanked them profusely and bid his final goodbye to his daughter, who was now in tears.

"Lord Sekiro, I suggest you also relocate to a new place. Tonight is the night the leader of the demons was planning to attack." Musashi said as he left the family's home. With that, the family packed all of their stuff and left. Once they reached a large hill that overlooked the entire region, they all glanced at the Musashi manor being set ablaze. Rem was in tears and wiped her eyes as she saw her old home in flames. Emma Knelt down and hugged Rem, who began to cry uncontrollably.

"Poor girl, everything she had is being taken away from her." Kuro said solemnly looking at the blaze.

"Rem-chan, we promised your Otousan that we will look after you and protect you from those monsters so stay strong." Emma said, wiping away Rem's tears.

"I know, I just miss papa and mama." Rem said in between sobs. (Y/N) feeling bad for the girl walked up to her and began to speak.

"Rem-chan, everything will be alright. I promise I'm going to do everything I can to protect you from those monsters and avenge your parents." Rem looked at (Y/N) and wiped her eyes.

"Do you promise?" Rem asked as (Y/N) hugged her.

"I promise."

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And the first part is done. I hope you all enjoyed it and feedback is welcomed.