The movie takes place on one of the smaller islands of Japan. A small mining operation is in a panic; the mine's deepest vein has flooded, and one of the miners was found horribly mutilated. The blame falls upon Goro, the last person the dead miner was seen with. Goro's friend Shigeru, determined to prove Goro innocent, discovers that the killings were actually done by prehistoric insects. Shigeru leads a group of soldiers into the mine, where they battle the monsters. When bullets prove ineffective, Shigeru kills the bugs with a booby-trapped mine cart. With the monsters that did the killing dead, the movie's over, right?
As the cart explodes, the mine shaft collapses, trapping Shigeru inside. Meanwhile, a nearby volcano has become active, endangering the village, and to make matters worse, UFOs flying at supersonic speeds have been sighted all over the world, attacking jets and carrying off a young couple visiting the mountain. Meanwhile, Shigeru has been found outside the mine, badly hurt and suffering from a total loss of memory. Weeks go by, the UFOs are sighted some more times, and Shigeru's memory slowly returns. When his fiance Kiyo shows him that eggs her pet birds laid are hatching, Shigeru suddenly remembers what happened to him.
As it turns out, when he got trapped in the mine, Shigeru fell into the nest of the killer insects. Inside this nest was an egg, which promptly hatched, revealing a giant flying reptile, which ate the remaining bugs before taking off. A scientist who hears Shigeru's story and examines all the collected evidence about the mystery of the UFO, realizes that the monster and the UFO are one and the same, a mutated descendant of Pteranodon called Rodan. Army guys show up, and discover that Rodan is living in the volcano, and what's more, it's not alone. A second, female Rodan flies out of the mountain, and joins her mate in leading the military in a chase across Japan, finally landing in, and leveling, Sasebo.
After the attack, when the Rodans have gone back to the volcano, the military comes up with a final, desperate plan to defeat the monsters. The plan: Set off the volcano, with the Rodans still inside. As the mining village is being evacuated, Shigeru finds Kiyo near the volcano, and tells her that he loves her, and that they should probably get out of the way of the volcano. Not a moment too soon, either, because as they leave, the army moves in. Bombers attack the Rodans' nest, and ground-launched missiles set off the volcano. When the Rodans fly out of the erupting volcano, all hope seems lost when, suddenly, one of the reptiles succumbs to the volcanic fumes. As the military, Shigeru, and Kiyo look on, the male Rodan flies into the eruption, choosing to die rather than be separated from his mate. As Shigeru ponders the implications of such actions in supposedly "vicious" monsters, he wonders whether he could ever make such a sacrifice for Kiyo, and we fade to black.
Ever since his debut in this film, Rodan has become a frequent part of the Godzilla franchise, having appeared in many films alongside the Big G. He's usually portrayed as an ally of Goji out of sheer convenience, and as such doesn't have as much of a friendly interaction with The King of the Monsters as other kaiju like Anguirus. Easily recognizable on his own, the big, angry pterosaur has successfully cemented his place as one of the most iconic kaiju from Japanese pop cultue.
This film provides examples of:
- Always a Bigger Fish: The Meganulon go on the rampage... then the Rodans emerge and eat them as HATCHLINGS.
- A-Team Firing: Although the Tank corps manages to land a few hits on the grounded Rodan during his raid on Fukuoka, every single missile truck manages to completely miss the giant creature standing barely a thousand yards away!
- Bittersweet Ending: The destructive Rodans are stopped in the volcanic eruption, but the characters all appear to feel quite shitty about how it went down, watching on mournfully as the Rodans burn to death together.
- Canon Immigrant: Rodan eventually made his way into the Godzilla films.
- The Meganulon themselves reappear with a more significant role in Godzilla vs. Megaguirus.
- Clear My Name: A man is accused of murdering a man who he is feuding with. Killer insects are at fault.
- Cosmic Horror: Being an early Kaiju film, there is a distinctly Lovecraftian influence on the monsters.
- Destructive Savior: The vast majority of the damage inflicted in the battles against the Rodans is caused by the JSDF, due to their utter inability to hit a moving target. The Rodans don't actually do any intentional damage, all the destruction they cause is from the downdraft of their wings as they pass by.
- Disc-One Final Boss: The Meganulon are the primary threat for the first part of the movie, but after they're destroyed, the Rodans emerge and go on the rampage themselves.
- Dub Name Change: The City of Fukuoka is changed to Sasebo, Nagasaki for the U.S. release. The volcanic Mt. Aso was changed to "Mt. Toya" for whatever reason. Rodan's name is actually pronounced "Radon" as in Pteranodon in the original release.
- Dug Too Deep: Both the Meganulon and the Rodans are awakened during a mining operation.
- Early Installment Weirdness: While grounded and attacked by the military in Fukuoka, Rodan fights back with a high winds Breath Weapon. It's the only time in the Showa era that this is used. The idea is revisited in the Heisei era, becoming a heat ray in Godzilla vs. Mechagodzilla II.
- Easy Amnesia: Sort of. The amnesia happens after a terrible head injury and it takes several weeks to recover, but once Shigeru does he remembers everything he's seen.
- Giant Flyer: Rodan flies so fast as to use his sonic boom as a weapon.
- Giant Equals Invincible: Averted. Both monsters die by falling into a volcano while the JSDF bombs the area with an air strike.
- Green Aesop: The Rodans and Meganulons alike are disturbed by over-zealous coal mining.
- Immune to Bullets: The Meganulon. Except for their undersides.
- Meaningful Name: Rodan's Japanese name "Radon" is a reference to what he is, a mutated "pter-RA-no-DON."
- Ptero Soarer: Rodan. Justified, in that he isn't supposed to be realistic in the first place.
- Reality Ensues: Rodan merely flying over your city displaces his weight downward. It's not quite a Colony Drop, but it does the job.
- Recycled In Space: It's a tragic love story, with Kaiju as the two ill-fated lovers. In the original release very little emphasis is placed on the female Rodan, and it is not made clear if that the two creatures are mates.
- If both Rodans hatched from the same location, it would probably make more sense that they were both from the same clutch, and therefore would be siblings, rather than mates. The original Japanese version doesn't clear this up either way, however.
- Slurpasaur: A very creative example. The scene of the baby Rodans eating the Meganulon? The bug monsters were crayfish dressed in tiny costumes!
- Stock Footage: Much like the U.S. release of Godzilla Raids Again, the distributors felt the need to add a prologue with stock footage of Hydrogen Bomb blasts and Fauxlosophic Narration. This emphasizes Rodan's origin, for even in the original Japanese cut, it was explained by Professor Kashiwagi (the military's biologist) that the Rodans may have been awakened by radioactivity from bomb testing seeping through the cracks of their mountain home.
- Additional stock footage is used elsewhere, such as the fighter jet take off sequence.
- Tertiary Sexual Characteristics: Used in a more realistic sense. The male Rodan is of a dark, reddish color scheme while the female is more brown.
- Together in Death: The male Rodan chooses to die alongside his mate after she dies in a volcano.
- Too Long; Didn't Dub: Almost every instance of the Japanese honorifics "san" and "chan" are retained in the English dialogue.
- To Serve Man: The Meganulon and Rodans both eat people throughout the films.
- Your Princess Is in Another Castle!: The Meganulon are destroyed... only for it to turn out their predators have awakened as well.