You are the Shinazugawa's little sister and you wa fighting a demon until they turn you into a 1 year old and as a baby let's say that you always been a calm baby and Mitsuri and Shinobu and the other hashira's your besties heard what happened even the Kamado trio's and Mitsuri do morning shifts and Nezuko do night shifts to protect her and Shinobu and like a medical doctor for you and the rest of the them are thinking and aoi makes sure inosuke does not make you cry and sometimes you cry at night time an Nezuko always knows what to do because she wa not born yesterday