Terror of Mechagodzilla, is a 1975 Tokusatsu Kaiju film.thumb|300px|right
Continuing after the end of Godzilla vs Mechagodzilla , Interpol agents, led by Inspector Kusaka, search for the wreck of Mechagodzilla at the bottom of the Okinawan Sea in the submarine, Akatsuki, to gather information on its builders, the aliens of the third planet from the black hole. But, the Akatsuki is suddenly attacked by a giant aquatic dinasour called Titanousaurus, and the crew is apparently lost.
In response to the incident, Interpol begins to investigate. With the help of marine biologist Akira Ichinose, they trace the incident and Titanosaurus to a reclusive, mad scientist named Shinzô Mafune, who was forced to leave the institute, and now wants to destroy them as well as all of mankind. When visiting his old house in the seaside forest of Manazuru, they meet Mafune's lone daughter Katsura, who tells them that not only is her father dead, but she also burned all of his notes on the giant dinosaur (at her father's request). But unbeknownst to them, Mafune himself is alive and well, visited by his scientist friend Tsuda, who turns out to be an aide to the new black hole alien leader Mugal, who is leading the project to quickly rebuild Mechagodzilla. Mugal offers their services to Mafune, so that his Titanosaurus and their Mechagodzilla 2 will be the ultimate weapons. The ultimate goal of this new wave of black hole aliens is to wipe out mankind and rebuild cities around the world as a high-tech dystopia.
But things are complicated for both factions when Ichinose falls in love with Katsura, and unwittingly gives her Interpol's secret information against Titanosaurus, the new Mechagodzilla, and the aliens. We also find that Katsura is actually a cyborg, and Mugal may have use for her. Meanwhile, Mafune is desperate to unleash Titanosaurus without the aliens' permission, so he releases it on Yokosuka one night. By then, Interpol discovers Titanosaurus' weakness: supersonic waves. But when they construct a supersonic wave oscillator, Katsura sabotages the machine, prompting Interpol to hastily repair it; Godzilla arrives to fight off Titanosaurus.
Later, Ichinose goes to visit Katsura, but is captured by the aliens. Tied to a chair, Ichinose can only watch as Mafune and the aliens unleash Mechagodzilla and Titanosaurus on Yokosuka, while Interpol struggles to repair their machine and the Japanese armed forces struggle to keep the two monsters at bay. Katsura, whose machine core is being fully manipulated by Mugal, ignores Ichinose and controls both the dinosaur and the robot as they destroy the city.
Godzilla comes to the rescue, though he is outmatched by the two titans. While Interpol distracts Titanosaurus with the supersonic wave oscillator, Godzilla is able to focus on attacking Mechagodzilla. Interpol agents infiltrate the aliens' hideout, rescue Ichinose, and then kill Mafune and much of the aliens. The remaining aliens attempt to escape, but Godzilla shoots them down. Katsura, while being embraced by Ichinose, shoots herself to destroy Mechagodzilla. Godzilla, with the help of the oscillator, kills Titanosaurus and heads off back to sea.