(Update 2/11) You is Yoriichi's siblings, you and Michikatsu always having arguments about stupid stuff while Yoriichi just stay calm because he used to it

You two were attacked by a demon at home and turned into demons. You two wanted to attack the Kamado family(Sumiyoshi) and Tsugikuni's family. But Yorichii managed to stop you two

Yoriichi will drag you both anywhere and let you both alive as he try to find way to make you both back to human

It was now the taisho era.

Yoriichi is trained the demon slayer at the backyard, he is wearing the demon slayer suit while watching over you two on Engawa that having arguments as usual. He find it normal

Yoriichi just continue to trained Tanjiro since he's also sun breathing user so he can teach him about it

Yoriichi know that Tanjiro's young sister. Nezuko, is demon but she can go under sunlight because she have eat blue flower spider lily before she turn to demon. He knows Tanjiro is Kamado family.