Kagaya Ubuyashiki

The 97th head of the Ubuyashiki family and leader of the Demon Slayer Corps. 23 years old. Referred to as "Master of the Mansion" by the corps members, he calls the demon slayers "my children."

Belonging to a family cursed with short lifespans and illness, the skin on the upper part of his face is altered. By the time of his first appearance at the Pillar Meeting, he has lost his sight. As time progresses, his illness advances, and his body weakens. His voice has a "1/f fluctuation," which soothes and uplifts those who listen. Even the Pillars, who are too strong-willed and individualistic to unite, all revere and admire him. Aware of the demon Nezuko's existence, he tacitly approves of Tanjirou's actions. He does not outright dismiss the Pillars' opinions of autonomy and sense of duty, and eventually, he officially acknowledges Nezuko within the organization. He also secretly knows about the existence of Tamayo among the Pillars.

In fact, he is a descendant of the family that produced the demon Muzan Kibutsuji a thousand years ago. He views the family's illness as a curse resulting from the sin of birthing Muzan, and has maintained the Demon Slayer Corps and the short-lived bloodline through sheer determination for a millennium. Despite his frailty, he is highly intelligent and supports the Demon Slayer Corps with his wealth. Defeating Muzan is his family's fervent wish. It is said that his and another's faces are "as alike as two peas in a pod." During the Entertainment District Arc, he vomited blood but rejoiced at the defeat of the Upper Rank Six demons by Tanjirou and others.

He had kept the location of his mansion hidden, but Muzan eventually discovered it. Due to the progression of his illness, he could barely speak when he finally confronted Muzan. However, he had anticipated Muzan's arrival and had prepared a plan to use himself as bait to defeat Muzan. In the face of Muzan, who seeks eternal life, he spoke of "human emotions" as "the truly immortal," and with the words "Thank you, Muzan," he and his wife and two daughters committed suicide by explosion. Muzan had sensed a trap but had not anticipated that he would take his family with him in a suicide attack, remarking that "that man is completely off the rails."