Tsubasa Nishikiori

The landlady of the Kurogane House, a spa in Atami. She and her staff has a mysterious connection with the Kabuto family as well as a vast knowledge about Dr. Hell and the Mycenaeans.

Tsubasa was originally a character from Gakuen Taikutsu Otoko as a high school student opposing the oppressive teachers with great physical strength and becomes the proprietor of a bathouse with strong fighters to help out. She also appears in Susano Oh with a similar role.

Tsubasa also appeared in several other Go Nagai manga such as Violence Jack's City of Gold arc where she is the leader of a yakuza gang that assist the title character, here Tsubasa is portrayed as an adult bearing the age and appearance that would be used in Shin Mazinger.

(Source: Wikipedia, fandom)