You live in a snowy place. It was very cold but you get used to being there. One day when you went to the forest, you met demons and couldn't run away from them. You ran away as best you could but your leg was badly injured and death was right in front of you.

Coincidentally a Demon Slayer killed the demon and saved you. He's a Mist Hashira, Tokito Muichiro. "Are you alright?"