Yay! for this movie. Re-watched it last night. It, along with Son of Godzilla, represent a truly awesome aspect of the Showa films. The idea that monsters are commonplace is seen in things like the fairies appearance on television in Ghidrah, the Three Headed Monster is awesome. However, this film, and the next, take that to the max. The story at the heart of this is just that a couple of random people end up on an island that is one HQ for a terrorist organization.
It's so great. It's maybe not as mundane as the scientific research on an island plot of SOG (which I prefer to this film), but I really dig the idea of a Godzilla film driven by entirely crazy/yet plausibleish stories. Before, in things like Monster Zero and Mothra vs. Godzilla, humans/aliens directly affect the action, but it's always through manipulation of the monsters. Here, and more so in SOG, the story is wholly separate from the kaiju (Unlike MvsG and MZ in which the kaiju are key). Mothra is somewhat key in being the means of escape, but that's it.
"We Can't Stop Here, This is Bat Country!"