Kamen Rider 1 through RX: Big Gathering

A nuclear explosion in the far north unleashes Gamera, the legendary flying turtle, from his sleep under the ice. In his search for energy, Gamera wreaks havoc over the entire world, and it's up to the scientists, assisted by a young boy with a strange sympathic link to the monster, to put a stop to Gamera's rampage.

Gamera escapes from his rocket enclosure and makes his way back to Earth as a giant opal from New Guinea is brought back to Japan. The opal is discovered to have been an egg that births a new monster called Barugon. The creature attacks the city of Osaka by emitting a destructive rainbow ray from his back, along with a freezing spray capable of incapacitating Gamera.

An independent group of researchers called the Godzilla Prediction Network (GPN) actively track Godzilla as he makes landfall in Nemuro. Matters are further complicated when a giant meteor is discovered in the Ibaragi Prefecture. The mysterious rock begins to levitate as it's true intentions for the world and Godzilla are revealed.