After a spaceship transports Akio and Tom, two Japanese kids, to the Planet Terra, two Terrans take them to their base, and reveal that they are the last of their kind, decimated by the near-constant swarms of Space Gyaos which frequent the planet. They also reveal that the monster Guiron is their 'guard kaiju' of sorts, and send him out to battle a Space Gyaos. After Guiron defeats and kills the Space Gyaos, the Terrans' true intentions are revealed: they intend to kill and feed upon the kids' brains. Gamera arrives shortly afterwards, having chased the spaceship across the Solar System, and engages in combat with Guiron, being knocked out in the first battle after having his head lacerated by Guiron's shurikens. The Terrans now proceed with their plan, but the kids secretly let Guiron back out of his enclosure beneath a river. Guiron begins attacking the base, and ultimately the two Terrans were killed trying to escape, ending the era of the aliens on their planet.
- The Terrans are one example of a species or race which are directly named after the planet which they live on. A similar example are the Tsuburaya Baltans, which also reside on a planet which bears their name.
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