When six-year-old Y/n loses her brother to a demon, the 97th leader, Ubuyashiki Kagaya, ends up taking her in - caring for her as an older brother would. Swearing to protect her new family and friends, little Y/n promises to become a demon slayer and kill every demon. However, when years pass by and Tanjiro and his demon sister Nezuko arrive, Y/n ends up wanting to protect two more people. - I do NOT own Demon Slayer or its characters, I only own this fanfic's plot and my OCs.