If you didn’t know that this is all rehash, you might just enjoy yourself. Gamera: Super Monster contains extensive stock footage of the entire Gamera film series, as well as 1977's Space Battleship Yamato and 1979's Galaxy Express 999. Almost all the footage of Gamera is stock footage. The movie is therefore hard to keep up with, but it’s not all bad.
If you’ve seen any of the films Gamera: Super Monster borrows material from, then don’t bother with this. The illusion simply won’t work. The bad editing doesn’t help. There is an overwhelming clash between what some of the protagonists spend their time doing and the monster attack; between the immensity of the kaiju invasion and the kid setting his turtle free then playing piano, for instance.
There is a fine line between recycling and garbage. That line has been crossed. The alien transformation sequences are ridiculous and borderline useless. Why magically change your wardrobe only to dodge lasers and turn back to human form seconds later? Is this bad editing or is it bad storytelling? You’ll spend this film watching the clock. It’s not a long movie, but it seems to last an eternity.