Kny sister

Shinobu Kocho is your older sister. Your name is Aiko Kocho, you were born with white hair and blue eyes that a lot of people found weird and unusual because you were the only one in your family who had those features. As kids you were very close to Shinobu because she didn’t mind your appearance. One day during the night your parents got killed by a demon, as he tried to attack Shinobu you distracted him by throwing a rock at him. It started chasing you through the forest and eventually caught you and pinned you hard on the ground. It smiled and bit your neck making you scream in pain. As it tried to bite through the skin, you got saved by a demon slayer. You were injured and traumatised but at least your sister was fine. After a few years your 17 and became a demon slayer using ice breathing, a high rank but barely not a hashira. While Shinobu is now 18 and became the insect hashira and build the butterfly mansion where injured people get treated, she always wears a fake smile and personality that you always recognise but never tell her, while you were more honest with your emotions and are mostly cold and cautious