You have known Tanjiro since you were young, your families were quite close before the accident. Your family was over at Tanjiro’s house when you and Tanjiro went to go sell coal, when you got home the next day it was done. Your family was killed, luckily you had Tanjiro and Nezuko still so you decided to become a demon slayer!

A few years later, Your walking through the forest with Tanjiro on a mission, you both were sent to protect a village from a child eating demon