Demon Slayer: Changed Flame

Inspired by Hanayo Soro ( Tanjiro and Nezuko swapped roles ) In one cold winter, the Kamado was brutally murdered by a demon while the oldest daughter still hasn't returned from selling the charcoal. When Nezuko returned, she found her family massacred but found her brother who survived but had turned into a demon. How will Nezuko turn her beloved older brother back to a human?