Godzilla vs. Redmoon would have been a collaboration between Toho Studios and Tsuburaya Productions. The production staff, under the direction of Kazuo Sakawa at Tsuburaya Productions, would have reportedly provided the suits for the new monsters, while Toho would have loaned the MusukoGoji suit from Son of Godzilla for the film. When plans for the film fell through, its script was heavily altered and repackaged into the film Daigoro vs. Goliath, which was also a collaborative film, produced by Tsuburaya and distributed by Toho.
At the same time two yong pen-pals meet. They are Tokyo boy Ippei Suzuki and Ryukyu islander Agari Minoru. They have a love of snakes, and Agari has made a fascinating discovery that snakes on his home island of Habu Island have such longevity thanks to absorbing special tree sap. Ippei shows this to his uncle, newswriter Shoji Uchida, who mounts an expdition to the island, bringing them together. However, the two boys discover a plot by a greedy prospector named Onassis to capture all the snakes to make elixirs. However, another kaiju to emerges, only more docile. This new monster is dubbed Erabus.
A greedy news editor convinces the Japanese Self Defense Force that the two monsters should be led to one another in the hopes that they will kill each other. The plan is a success; however, instead of fighting, the two monsters mate, and it's revealed that Erabus and Redmoon are a female and male, respectively, of the same species. Erabus then gives birth to Hafun.
With the situation only getting worse, the JSDF is scrambling to create a new strategy to deal with the kaiju. Things go from bad to worse when Hafun is kidnapped by Onassis. Shortly after getting kidnapped, Hafun dies during the moving process. With their child dead, Redmoon and Erabus go berserk and start rampaging the once peaceful Okinawa. Having sensed the two from the beginning, Godzilla finally arrives and battles with the two kaiju, emerging victorious and bringing peace back to Okinawa.
- Other than the screenplay, very else is known about Godzilla vs. Redmoon, including the design of the three new monsters. For years, it was thought that Erabus and Redmoon would simply reuse the suits for Daigoro's Mother and Goliath from Daigoro vs. Goliath. However, this is inaccurate, as Godzilla vs. Redmoon was considered prior to the production of Daigoro vs. Goliath, and eventually evolved into the latter film. Currently, the best known sources for the monsters' appearances comes from artwork drawn by Hurricane Ryu Hariken several years after the film was scrapped.
- The main idea of the film, where two different-looking monsters (who are male and female of a sexually dimorphic species) appear separately and meet each other to mate, appears the 2014 MonsterVerse film with the MUTO, though this is likely a coincidence.
- In Septamber 2019, a translation of the film's story was published on Toho Kingdom. The story can be found here.