In a way, I think the old Gamera is the Japanese giant monster version of that famous canine, Lassie! As I've been a fan of Lassie since watching the TV show (also aware of the original Eric Knight novel that started it all), I have some comparisons to make:
-Lassie was originally the pet of British child Joe Clarracough (the character played by a very young Roddy McDowall!), whose unemployed father was forced to sell the dog to pay for the rent and food. Lassie escapes her new owner, the rich Duke of Rudling (who lives far away), and crosses all sorts of dangerous lands to return to the family she loves. This was the story of Lassie, Come Home.
-In Giant Monster Gamera, young Toshio Sakurai (Yoshirou Uchida) had a pet turtle named Chibi, which he loved dearly, but his father and older sister wanted him to get rid of it, because it made him an outcast and neglect his schoolwork. However, he also has the same empathy for Gamera, as he was a turtle as well. He failed to stop the JSDF from trying to destroy Gamera, or ultimately launching him to Mars in the head of a rocket (the Z Plan), but one thing was for certain, Gamera returned to Earth (in Gamera Vs. Barugon)!
-Since the famous 50s TV show, Lassie saved children (usually her owners) and the weak from disasters, criminals and bigger, hungry animals (which she would usually chase away or have a dogfight with).
-Gamera was a friend of children, saving them from danger as well as conventional foes like prehistoric creatures, space monsters and sinister aliens.
Whether it's a long-haired collie like Lassie or an atomic-powered giant flying turtle like Gamera, both are champions for children, as well as the weak and helpless! Everyone needs a hero, even if it's not a human.