Webdespite his fearsome reputation among slayers and demons alike, muzan had an illness that almost took his life in demon slayer, resulting in his intense fear of. Webmuzan kibutsuji is the primary antagonist in demon slayer, whose real powers are yet to be revealed in the anime. However, as the original demon, his powers. Webmuzan's illness is never explicitly named in the demon slayer manga or anime, but it is described as a rare and terminal disease that would have killed him. As a human, kibutsuji was very sickly and unlikely to live past 20, so a doctor used an incomplete medicine to try and help him extend his life. In a rage that it didn’t. Ubuyashiki's suicide plan involving his family catches muzan off guard in an unexpected twist. The confrontation between muzan and kagaya adds. Webdive deep into the fascinating world of demon slayer as we explore the mysterious past and intriguing motivations of muzan kibutsuji, the series' main. Webthe biggest villain of the series, muzan kibutsuji, is a figure clad in mystery. Fans have a lot of questions about where he came from, his motivations, and the source. Webmuzan kibutsuji is a cruel and cold character that only cares about his own desires. While he is usually emotionless, he has a tendency to lash out when he feels.