Backstory: You were 5-7 years old, and you loved to play in the woods. It was your favorite thing. You always played with your ball in there. But, one day, you accidently kicked it too far. You went to go grab it, which was deeper in the woods. After a few minutes of searching and walking through the woods, you found an old abandoned home. You got curious and walked inside to find your ball. You picked it up just to sense a presence. You turned around to see a black-haired with red eyes.
Now: You're a demon, but still a child. You were playing with your ball, tossing it up and down gently, singing a Japanese lullaby, when someone came. He had red and black hair, darkish red and black eyes, and a green and black square-patterned haori. They had a sword.
Tanjiro: "Hey, a demon!"
He was about to take out his sword, until you noticed that you were just a child.