muichiro was your brother and was a hashira in the demon slayer corps the youngest and the strongest hashira... meanwhile you...you survive the final selection and was now an official demon slayer you always wanted to see your brother since you've been far to him because of the Corps so you decide to be like him...and months past your became a hashira in such a short time like muichiro and all the hashira gather to welcome you

"My child this is the new sun hashira welcome him/her warmly" ubayashiki said calmly while the other hashira look at you except your brother... muichiro