you was Muzan's daugter, you were also a demon and needed to get stronger

You were also a shapeshifter, like your father, even though you couldnt change your clothes with your shape, so you were currently sitting, wrapped up in Kokushibo's haori, in your form without your clothes, he was holding you close and giving you a piece of human flesh

"You really need to get stronger little one" he said quietly, keeping you close, sinse Muzan tasked him to take care of you