In a snowy mountain forest stands alone a house in which the Kamado family lived.
The family consists out of seven members excluding the father, Tanjuro Kamado, as he died not too long ago because of a sickness.
The mother, Kie Kamado, took care of the children together with Nezuko the second oldest child and oldest daughter of the family while the oldest child, Tanjiro, goes to the nearest village to sell firewood in order to make enough money for his family.
Early in the morning Tanjiro loaded his basket with firewood in preparation for his trip to the village, he just said goodbye to his family and is currently walking through the snow.
The thirteen-year-old boy with dark brown hair which he pulled back into a short ponytail and the scar on his forehead stomps through the cold snow while wearing a black and green checkered haori.
He stops when his dark red eyes see someone coming towards him.
Before he could say anything, he heard the voice.
"Tanjiro!" The girl coming towards him is his younger sister Nezuko, she wears a light pink kimono with asanoha pattern and a white cloth which she uses to carry a young boy on her back.
"Ah, Nezuko." Tanjiro smiles upon seeing his little sister who has her long hair bound into a strict bun.
"I was busy putting Rokuta to sleep so he wont make a scene when you leave." She says before looking over he shoulder to the little boy.
"He really misses dad." After that they soon said their goodbye and Nezuko watches her brothers back slowly disappearing in the distance.
'So it is finally time.' Nezuko's face turns serious for a moment before returning to normal.
'Twelve years of waiting and preparing and it is finally time.' She takes a deep and calming breath in order to keep the nervousness away.
Nia Hill, a normal woman who lived her live on earth in peace till she died in car accident and reincarnated into the fictional world of Demon Slayer as the protagonist's little sister Nezuko.
At first it was hard to accept but Nia could pride herself in her adaptiveness as not even a week after her reincarnation she already came to terms with it.
In her previous life on earth she had read the manga and watched the anime of Demon Slayer so she understood her situation and the world in which she now lived in good enough to make some plans.
The first thing she did was to learn the dance of the fire god from her father which in truth was the first breathing technique, sun breathing, created by the legendary swordsman and demon slayer Yoriichi Tsugikuni.
While trying to learn the breathing technique something unusual happened.
Nia, or Nezuko now, started to see colors.
Strange glowing colors inside the bodies of people, animals and even plants.
Together with this new ability Nezuko also gained a terrifyingly accurate intuition to the point where she figured out the truth of her ability within mere days and mastered it within a week.
Her eyes can perceive a special kind of energy.
Every living being has some so Nezuko decided to just call it life-force.
After observing the life-force inside people, animals, plants and herself Nezuko started grasp the miniscule movements colorations and amount of the life-force in living beings and translate them.
The movement of life-force is directly connected to the body's movement and intentions while the coloration reveals the condition, the purer and deeper the color of your life-force the healthier you are in body and mind.
As for the last one, Nezuko only found out about its effect after she continued learning the sun breathing technique.
In her previous life there had been quite a few debates about the special effects that appear whenever a breath user used his techniques and their respective element manifested.
Some said that it was just a visual effect and that it wasn't really there, but there are just as many who rebuked this.
But all this doesn't matter anymore, after all this world wasn't the same as the one she read about.
Her existence alone was enough to prove that this wasn't the same one, so she didn't have any problems accepting the explanation that was reveled in front of her special eyes.
Aura, that is what Nezuko calls it.
The breathing techniques allow one to produce aura which can take different forms depending on the technique used to draw it out from one's life-force.
And that exactly is where the amount of one's life-force comes into play.
Depending on the amount of life-force one has the more aura one can draw out of it and use more techniques or concentrate more aura into one's attacks.
Thanks to her overpowered intuition Nezuko didn't take long to master the basics of sun breathing, but when she practiced it in secret, she realized that this breathing style wasn't a perfect fit for her.
Of course it wasn't, she after all wasn't Tanjiro, the successor of Yoriichi.
This realization pissed her off for some reason, but she soon calmed down again and after mastering all twelve different forms of the style she moved on onto the next step of her plan.
The see-through world, this technique which allows one to see through the surface of living beings and observe their muscles, joints and blood vessels is very powerful, but Nezuko is already able to see the life-force of people which allows her to achieve similar if not even superior results.
She learned it anyways as it was one of the abilities belonging to Yoriichi and it was the main reason as to how he created his and guided others to develop the breath styles.
By the time she mastered it, Nezuko just became twelve.
Entering the wooden house Nezuko greets her mother who wears a white clothe around her head and an apron over her haori.
"Did you manage to say goodbye to your brother?" Kie asks her daughter who just entered with a sleeping Rokuta on her back.
Smiling softly Nezuko walks past her mother in order to lay her brother to bed.
"I met him on my way back." She answers in passing.
The rest of the day quickly passed and Nezuko soon found herself cooking dinner while her mother was outside to do something.
Nezuko didn't have to look around in order to grasp the positions of all her family members.
Her senses have already sharpened beyond those of a normal human.
She swiftly takes out a small bag out of her sleeve and pours the content into the prepared food.
'I wont let you be die today, so please forgive this dumb daughter and idiotic sister.' Guilt rose up inside her eyes but she covered it up immediately.
What she just poured into the food was a strong sleeping medicine which can knock one out for a good ten hours.
With twelve years to prepare for this moment, Nezuko of course had everything prepared already and was only waiting for the time to arrive.
A few minutes later the entire Kamado family except for Tanjiro who slept on the foot of the mountain in the hut belonging to Saburo came together to eat.
"Oh! I forgot something outside." Just before the started eating Nezuko stood up and made a apologetic expression.
"You guys can start without me, I'll be back in but a moment." Without letting any of them time to say something she runs out side where she lets herself fall into the snow while leaning against the wall of the house.
'Im sorry! Im going to worry all of you. Tanjiro will be sick with worry about your whereabouts while the rest of you will have to worry about my and Tanjiro's wellbeing. Im sorry, but Im going to try and clear everything up as soon as possible without dooming the world.' Rolled up in a ball Nezuko apologizes while some tears run down her cheeks.
She couldn't just run away with her family, because that would ruin everything and the whole plot of the Demon Slayer story will go down a terrible path without the protagonist.
Because of that Nezuko had to come up with some kind of plan in order to safe her beloved ones while not dooming the rest of the world.
In the end she decided to put her family to sleep and hide them away in the faithful night.
This way Tanjiro wont experience the same horror and despair as in the original story, but their disappearance hopefully will be enough to fuel him enough so that he can overcome all the terrible things fate has prepared for him.
Of course Nezuko also hoped that Muzan