Muzan, the main antagonist of Kimetsu no Yaiba by Koyoharu Gotouge, is on a relentless quest to eradicate humanity. Consequently, he is particularly focused on eliminating the Demon Slayer Corps. If there is only one way to ensure the survival of his kind, it is to dismantle this organization, which would help him dominate the world without facing much resistance.
Thus, Muzan directs his attention towards Ubuyashiki Kagaya, the leader of the Demon Slayer Corps, with the hope that eliminating him will lead to the disbandment of the organization. Unfortunately for the demon king, this task proves to be more difficult than anticipated.
The enigmatic character in Kimetsu no Yaiba reveals a shocking possibility within the series: Muzan might actually seek out Ubuyashiki. But why is this the case? The answer lies in Ubuyashiki’s lineage. Historically, the leaders of the Demon Slayer Corps have been targeted by Muzan.
In truth, this answer is not explicitly detailed in the manga or anime but is found in the supplemental content of Volume 21 of the manga. According to the author, the previous leader of the Demon Slayer Corps was defeated by the Upper Moon One, Kokushibo. The Upper Moon One attacked the headquarters of the Demon Slayer Corps, taking the life of the former leader (who is also Ubuyashiki Kagaya’s ancestor) and bringing his blood to Muzan.
Moreover, the residence of Oyakata has always been heavily guarded. This has led to the formation of Kakushi, a group that operates much like the stealthy guardians of the Demon Slayer Corps. Their task involves maintaining secrecy, ensuring safety, and acting as spies for the Butterfly Mansion. This group has helped to hide the whereabouts of Ubuyashiki, the leader of the Demon Slayer Corps, as well as the location of the Butterfly Mansion.
In Season 3, Episode 1 of Kimetsu no Yaiba, Muzan reflects on the fact that Ubuyashiki is still alive, and Kokushibo reports that Ubuyashiki has hidden every detail of his existence.
However, in the final scenes, Muzan manages to uncover Ubuyashiki’s location with the help of Nakime. After receiving Muzan’s blood, Nakime’s ability to detect increases, allowing her to track Ubuyashiki by following a member of the Demon Slayer Corps.
By targeting the leader of the Demon Slayer Corps, Muzan hopes to weaken the organization and its Hashira.
The curse of Ubuyashiki Kagaya stems from when Kibutsuji Muzan—having shared blood with the Ubuyashiki clan—became the first demon. Since then, every descendant of the Ubuyashiki family has been fated to die prematurely due to this curse. As a result, Ubuyashiki’s lifespan has been significantly reduced. In reality, when Muzan finds Kagaya, he is already weakened and on the brink of death.
Interestingly, when he first encounters Kagaya, he attempts to create a diversion to catch Muzan off guard, eventually sacrificing himself for the sake of the Demon Slayer Corps’ mission to slay demons.
