Shinji Mafune is the main human/true main antagonist of Terror of Mechagodzilla.
He is portrayed by Akihiko Kirata.
Dr. Mafune is a mad scientist who became obsessed with studying brain patterns of marine life to the point of losing his academic credentials and being ridiculed by the scientific community. He was thought to be dead, but was revealed to be alive. As it turns out, he had become insane and, with the help of the Black Hole Planet 3 Aliens, gained control of Titanosaurus and reconstructed Mechagodzilla to get his revenge on humanity. In a strange twist of fate, his daughter Katsura had been turned into a cyborg that controlled both creatures and committed suicide, thus effectively ending his plan.
- Though Mechagodzilla reprises his role from Godzilla vs. Mechagodzilla, Mafune is the true villain because he initiated the plot by reconstructing Mechagodzilla.
- It is unknown what became of Mafune.