Masato Minami is a minor figure in the narrative of Kamen Rider BLACK, known primarily through his familial connection to the protagonist. He was the husband of Tomoko Minami and the biological father of Kotaro Minami. Masato Minami was a member of the secret organization Gorgom, which was responsible for his death. According to the story, Masato Minami and his wife were killed by Gorgom itself, making Kotaro an orphan at a young age. Following their deaths, Kotaro was adopted by Soichiro Akizuki, a professor who was also involved with Gorgom.

Masato Minami does not appear alive in the main events of the series. His role in the story is entirely retrospective, serving as a piece of Kotaro's tragic past. The revelation of his murder by Gorgom deepens Kotaro's resolve to fight against the organization and fuels his personal vendetta. There is no detailed exploration of Masato Minami's personality or motivations beyond his membership in Gorgom and his ultimate fate as a victim of the same group. Likewise, he exhibits no notable abilities, as he is depicted as a regular human who was killed before the series begins. His key relationship is his connection to Kotaro, which is defined by loss and the circumstances of Kotaro's origin. Masato Minami does not undergo any character development because he is deceased before the story commences. In the manga adaptation of Kamen Rider BLACK, Kotaro Minami's father is named Koun Minami, differing from the television series.