I am Muzan Kibutsuji i am most unsympathetic and his background of a demon all due to a sickness doesn't justify my selfishness and the cruelty that i created. Overall, Muzan is responsible for all the tragic events that happened within the story of Demon Slayer: Kimetsu no Yaiba. Most of the major demons are portrayed as tragic, instilling sympathy, and also showing insecurity, but Muzan never had any sympathetic qualities, having been utterly selfish and remorseless from the start.