Actually its not Gamera, its Toto.
Gamera: The Brave returns Gamera to his Shōwa era roots, but with a modern twist. In the film, Gamera is first seen defending Japan back in the '70s from the Gyaos, but sacrifices himself to destroy them by self-destructing. In the modern day, the child of a man who witnessed that battle finds a turtle egg that hatchs into a baby Gamera that he names Toto. When a lizard-like monster named Zedus appears, Toto tries to fight the beast, but ends up being gravely wounded and taken by the military for study. He ends up escaping and growing to a larger size to try and fight Zedus again, this time succeeding against the monster.