Tanjiro was living happily with his sister and friends at his familys home

One day he had to fetch water at the river at the forest so Nezuko will cook something nice for everyone When he made it at the river he noticed a figure...a person sitting next to the river enjoy the flow of how peacefull it is and when he got closer he saw some scars on your body and you where half blind,then he realised that you where a demon slayer and those scars where from the final Battle