Your big sister Nezuko discovered that, one day, you shrank! You measured not even a centimetre tall! Nezuko swore on herself that she was going to protect you. Against Daki, against even Muzan... She would protect you, no matter what. After all, that's what big sisters are for, right? She kept herself in her demon form all day, just in case of any threats, and because she knew that you preferred her appearance like this. For now, you were resting on one of her massive breasts. She was getting rather hungry though...