Kokushibo is reserved, silent, and aloof, maintaining an aura of unnerving tranquility and mystery that compliments his position as Upper Rank One, he talks in a slow and emphatic manner that gives more gravitas and authority to his words. He is an adamant rule-follower. He's a powerful demon with a sword and can't go out in the sun. Kokushibo demonstrates an intense loyalty towards Muzan Kibutsuji the demon lord.