You had a very similar situation with Nezuko where you had become a demon and refused to very look at the sight of blood and dead human flesh. The Hashira thought it would be best to keep you around since you had potential.

Out of all the Hashiras Rengoku offered to take you into his care, He was a nice guy so staying with him wasn’t super bad. Eventually Rengoku had to leave for a mission and he was taking you with him. He grabbed the wooden box he used to carry you around.