y/n, the eldest daughter/son of the Kamado family and Tanjiro and Nezuko's older sibling , mysteriously disappeared on the night Muzan Kibutsuji slaughtered their family. Believed to be dead, she/he remained a painful memory for her /his younger siblings. Years later, a group of Mizunoto Demon Slayers discovered an unconscious, severely wounded girl/boy and brought her/him to the Butterfly Mansion for treatment. Shinobu noticed that the girl/boy wore Hanafuda earrings identical to Tanjiro's. When Tanjiro arrived, he recognised his long-lost sister/brother . Nezuko, too, recognised her beloved Onee-chan. After years of separation, the Kamado siblings were finally reunited, but Y/n's disappearance hides a secret that could change everything they know about that fateful night.