Seikan Tokusou Assault Riser

Reporter Goro Maki stumbles upon scientists conducting weather experiments on Sollgel Island in the South Seas. He discovers the island is inhabited by giant mantis and a woman named Saeko who's been cast away since the death of her father. The pair soon find a helpless infant monster that Godzilla must adopt and learn to raise as one of his own.

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.