(Sora no daikaijû Radon)
In the mining city of Kyushu near Mount Aso, Japan, workers fear for their lives. The well has become too deep, with dangerous floods and landslides in the deepest parts of the mine. Two miners disappear in the depths of the mine, then policemen who came to their aid are found mutilated. That night, Shigeru Kawamura and Kiyo, two friends of one of the victims, are attacked by a monster coming from the mine.
A new rescue crew lead by Kawamura enters the mine in pursuit of the monster. They discover a great number of prehistoric giant dragonfly larvas, Meganulons whose incubations had been caused by the warming and the modification of the earth's surface. An attack by the monster causes a collapse of the mine's walls that buries them.
When an earthquake occurs, a depression that is created allows them to find Shigeru Kawamura, the only survivor and a victim of a total amnesia. When he gets his memory back, he explains that he was trapped in an excavation where he witnessed the hatching of a gigantic egg. As proof, the creature hatched from the egg must have immediately devoured the Meganulons of the mine, which were as small as worms to their predator. He confirms to the authorities the resemblance of the animal to a Pterodactyl and this causes panic to spread to cities across the continent. A piece of shell found by a scientific team allows them to determine that the beast is a Pteranodon that measures approximately 80m scale and outweighs 100 tons.
The beast (which they name Rodan) flies at supersonic speeds. Its destructive sonic boom ravages everything in its path. Repeated nuclear tests caused the awakening of Rodan after being in suspended animation for 200 millions years. While a squadron of jets attempts to destroy the Pteranodon without success, Rodan advances toward the city of Sasebo and causes massive destruction to the city's downtown area. The shocked population is evacuated from the city. When Rodan enters the center of Sasebo, the army assaults Rodan with all available artillery. Despite the massive fire power, Rodan escapes destruction, then another gigantic Pteranodon apppears. The two beasts continue their destruction and devastate the city of Yawata...
Spoiler ! the end of the story is revealed below…
The army knows that the monsters hide under Mount Aso. The nest of the beasts is found in the crater of the volcano. Despite the risk that the volcano might erupt, the decision is made to destroy the nest with the help of missiles and heavy artillery. As they had feared, the volcano erupts. The eruption of the volcano forces the two Rodan out of their nest and they die in a river of hot lava.
(Correction by Dave)