On the Topic You Asked For
There's a problem I need to get out of the way first. Muzan Kibutsuji is not a character in Jujutsu Kaisen. He is the primary antagonist of Demon Slayer: Kimetsu no Yaiba, written by Koyoharu Gotouge. Jujutsu Kaisen is a completely different series by Gege Akutami, and its central figure around whom the story revolves is Suguru Geto or Yuta Okkotsu depending on which arc you are talking about. I have read both series multiple times and watched the anime adaptations. Confusing the two is not uncommon for casual viewers since they share the supernatural shonen demographic and came out in similar timeframes. But they are unrelated. This matters because everything else you build on this premise will be wrong, and so would any guide I wrote for it.
The Dark King Unveiling The Fascinating Story Of Muzan Kibutsujis Reign In Jujutsu Kaisen
If you are looking for information about Muzan Kibutsuji, he appears in Demon Slayer. He is a demon king who has existed for over a thousand years. His story centers on his fear of death, his experiments on humans to find a cure, his leadership of the Twelve Kizuki, and his eventual confrontation with Tanjiro Kamado and the Demon Slayer Corps. There is no crossover event where he appears in Jujutsu Kaisen. Canonically, the two series share nothing. I ran into this same confusion myself when a coworker asked me to summarize "the Jujutsu Kaisen villain arc" last year and clearly had the characters mixed up. I just told them they meant Demon Slayer. It saved about twenty minutes of explaining that the Cursed Techniques in JJK have nothing to do with Muzan's Blood Demon Art or poison physiology. Both shows deal with supernatural threats, but the power systems, lore, and narrative structure are entirely separate. If you want a tutorial on Muzan's story in Demon Slayer, I can help with that. If you want a guide on the main antagonists in Jujutsu Kaisen, I can do that too. Putting the two together into one topic will only produce inaccurate information, and that is not useful for anyone actually trying to understand either series.
