The story starts up by showing us that the Z plan enacted in the first film pretty much failed right away as an asteroid frees Gamera who immediately comes back to Earth. Considering he can get back to Earth so quickly makes me think even if he had landed on Mars he still would have come back. Of course, he does not look up Kenny to see how his number one fan is doing, but rather he trashes a dam and then disappears for a while. During his absence, three men go to an island to find an opal. The villagers beg them not to go to the cave where it is stashed, but they do so anyway and one of the men promptly turns on the other two. One of them dead, the other rescued by the villagers. The one who escaped with the opal heads home, where a monster emerges from the opal as it was actually an egg! This beast immediately goes on the rampage! The man who was rescued by the villagers accompanies one of the villagers who tries to help defeat the beast, but it seems everything they try fails! The only hope may be the beast that once terrorized Japan, himself...Gamera!
This made for a good episode of Mystery Science Theater 3000 as I enjoyed the movie and the jokes. Gamera is not in this much, but I am sure the first time he appears there is a bit more of a fight between he and Barugon than what MST3K showed. Still, he is not in this one much considering he is the top billed monsters. He destroys a dam, fights Barugon and gets beaten and then returns for a quick fight at the end. Still, there is plenty to riff just watching Barugon do his thing and the humans do everything they can to stop it!
So, not a bad movie in my eyes, though my favorite film of the Gamera films during this era was the next film where Gamera fought Gaos. There were three films I did not see as they were never featured on MST3K which I can kind of understand as eight films in a series would kind of be overdoing it. Though two of the films would have probably made for good episodes, the final Gamera film would simply be kind of a compilation film where the battles of Gamera's previous films would be shown with some weird extra footage thrown in to make it look like a new film. After Gaos, the films did become more light than before and kind of goofy, but despite what others have said I do not really consider this one the darkest of the films, but it is the most somber.