GAMERA VS. GUIRON: Starry-Eyed Kiddie Lunacy From Another World
Two notable things happened to the Gamera series with its fourth installment, Gamera Vs. Viras: 1) it went from being kid-friendly to being totally aimed at the kids and 2) it became much more budget-conscious, with cheaper production values and recycled footage. The results were still fun but the reason why shifted as it upped the "dime-store surrealism" ante for the series. These trends continue in the fifth Gamera film, Gamera Vs. Guiron.
Once again, the film is driven by the exploits of two boys, one Japanese and one Anglo. This time, it's Akio (Nobuhiro Kajima) and Tom (Christopher Murphy), a space-obsessed pair whose desire to make contact with aliens becomes a reality when they see a spaceship land in a nearby wooded area. They outwit goofy but kind Officer Kondo (Kon Omura) to go to the site - and are promptly whisked away when they step inside the ship. In short order, Akio and Tom find themselves on a distant planet where two feminine aliens offer to get them back to earth.However, these aliens really sent their ship to earth to get some earth specimens to check out and are planning a hostile colonization of the planet (which involves humans becoming their livestock!). The planet also has a nasty monster named Guiron who has a large knife-blade for a head. Thankfully, the boys' journey to this planet 
has been tracked by the friend of all Earth's children, Gamera - but Guiron is a deadly foe and it will require a monster-on-monster battle to save both the boys and their home planet.This is definitely a lesser opus in the Gamera canon: the budgetary corner-cutting hinders the scope that made past series entries so much fun and also interferes with the quality of the effects (there a few really bad chroma-key visuals). Also, Gamera's screen time is limited in favor of the kids vs. aliens story. It doesn't help that both the heroes and villains are rather dimwitted (a reflection of the make-it-up-as-you-go scenario at play here) and that Murphy is one of the more stunningly inexpressive child actors you'll ever see. Overall, the story's aggressive targeting of pre-middle school kids gives it a saccharine quality that some cult film fans will find hard to stomach.
However, there are rewards for the Gamera lovers who stick it out: once the film gets to the aliens' planet, there are some cool miniatures to be savored and a bevy of cool monster battles. Despite the goofy kid-flick framing, Guiron is actually one of the more brutal and menacing villains of the series: he is introduced in a scene where he ritually dismembers(!) one of Gamera's past foes. There's also a twisted Brother's Grimm element to the alien plot, which involves the witch-like aliens plotting to eat to the young hero's brains.
Finally, it's hard to actively dislike a kid's film where adults are almost exclusively portrayed as clueless, arrogant or evil. In the fact, the only adult who gets sympathetic treatment in Gamera Vs. Guiron is Officer Kondo, because he is a childlike daydreamer who actually listens to the kids (in a crowd-pleasing moment for the kiddie audience, he scolds a couple of jerky reporters who mock Akio's little sister). Respect for kids and the need for adults to remember their childlike qualities are recurring motifs in the Gamera movies and this likely endeared these movies a great deal to their pre-teen audience.In short, Gamera Vs. Guiron isn't a kaiju-eiga classic but its eccentricities and themes make it an interesting view for schlock archaeologists. If you like your kiddie fare to be starry-eyed and demented all at once then you might find this film to have a certain wacked-out charm.