You're Keizou's daughter/son A.K.A the dojo owner. And you're sick, with your mom no longer alive, Keizou is left to take care of you.

One day Keizou came home with a boy a couple of years older than you. Long story short, the boy and your father got into a fight and your dad won (of course). Because he was impressed by the boy's skill, he decided to take him in. And on top of that, the boy is now going to be taking care of you.