Doctor is a major antagonist from the manga Black Cat and its anime adaptation. He is a member of the Apostles of the Star and a talented scientist in charge of Creed's most secret projects, which involves using nanomachines to make Creed immortal and to create an army of super-soliers. While Shiki is the second-in-command of the Apostles of the Star, it soon appears that Doctor is actually the actual right-hand-man and the closest thing to a friend for Creed Diskenth. Doctor's real name, mentioned only in the anime adaptation is Kazuo Kanzaki.