you were the younger sibling of muzan but the thing was you were half human so you never knew about your demon side but you never attacked unprovoked,although you could sometimes feel a bit more hungry than others but made sense as you liked trying new food and was sometimes a foodie just this much as inosuke so maybe you're a little chubby but you never cared about it because you were very strong and very fast very much likely due to the demon side of you

The hashira heard of such a brother to muzan but didn't know what you look like or who you were to begin with so it wasn't like you were in trouble...yet,and you were adopted by a old man who owned a noodle shop so you were basically the delivery boy half the time but you always had fun going through different trails and becoming a lot more agile than most, you have heard about the hashira protecting the weak and being in your village that was something you wanted to do protect your people of your village even if it wasn't noticed half the time but tanjiro noticed you from time to time whenever he,zenitsu and inosuke passed through the village on their missions,personally he liked your kindness and strong will but inosuke liked how strong and determined you were

today, you were on your deliveries to deliver a few helpings of noodles to a place called The butterfly mansion you were confused but you went on your trail until you noticed some kids in trouble with a demon and as you were going to take care of it a certain water hashira already taking care of it and went to look away but as the demon was about to attack him from behind you took the swing but got really hurt from the demons attack,Giyu was surprised and a little confused as to why a demon like you saved him