Katsura was the daughter of prominent marine biologist Shinzo Mafune. When her father was fired from the oceanographic institute, Katsura helped her father continue his experiments in controlling the monster Titanosaurus from his laboratory in their basement. Katsura was seriously injured in an accident in the lab, only to be saved by a group of mysterious men. Aside from just saving her life, the men turned Katsura into a cyborg. Katsura developed an ability to telepathically summon and control Titanosaurus, possibly through her cybernetic programming. Years later, the Black Hole Aliens, the "men" who saved her life, altered Katsura's programming to give her control over MechaGodzilla 2. Katsura struggled to retain her own free will and maintained a love interest with oceanographer Ichinose, who was studying Dr. Mafune's work. When Godzilla was battling MechaGodzilla, Katsura came to her senses and realized that only her own destruction would stop MechaGodzilla. She shot herself in the chest and died in Ichinose's arms, her sacrifice allowing Godzilla to triumph over his mechanical double.
Due to her cybernetic modifications, Katsura has several enhanced and superhuman abilities. She is capable of controlling MechaGodzilla 2 due to the controller installed inside of her. She seems to possess telescopic vision, observing Titanosaurus' attack on the Akatsuki underwater from miles away. At one point while pursued by INTERPOL, Katsura instantly disappeared, possibly due to either a teleportation or invisibility power. Katsura later was seen disorienting several INTERPOL agents with a flash of light from her eyes.
- In the English dub of Terror of MechaGodzilla, Katsura mispronounces Ghidorah as "Jeedrah", and Rodan as "Rayden."
- Katsura Mafune was portrayed by actress Tomoko Ai who is also known for portraying the character Haruko Matsuki in Ultraman Leo