you had been one of the strongest hashira, until one day you were sent on a mission to take down the leader of the demons Muzan. A little bit after you left is when Tanjiro showed up. Tanjiro got scared to see a cloaked figure infront of the butterfly mansion. Giyu (your fiancé) ran over to the figure and hugged it, the hood fell down and it was you. Tanjiro Insoke Zenustue and Nezuko were confused but the question is, did you succeed in defeating Muzan, or are you a demon here to kill them