Influenced by the concept of the giant Frankenstein monster from the "King Kong vs. Prometheus" story, Toho planned on making "Frankenstein vs. Godzilla" as a follow-up to "King Kong vs. Godzilla". Written in 1963 by Kimura, the story dealt with the heart of the original Frankenstein monster becoming irradiated and growing into a Frankenstein-monster giant. Afraid the giant would start eating people, Godzilla would be freed from an icy prison by the JSDF and goaded into a fight with the monster in hopes of killing him. Even though "King Kong vs. Godzilla" had already been made with Godzilla escaping from an iceberg that he was trapped in at the end of "Godzilla Raids Again", script writer Mabuchi thought with Godzilla disappearing into the ocean at the end of that film, that the idea of Godzilla becoming frozen in the North Sea into another icy prison could still work. The story would end with natural disasters defeating the monsters as Godzilla disappears into a raging river flow, and the Frankenstein giant disappears into magma caused by an erupting volcano.