It eventually had to happen, of course. Across four films from 1965-1968, Daiei's series of films about the giant monster turtle Gamera had ranged from not too bad, to not bad enough to stop being delightful, to bad enough that their badness made them delightful. But the tank had been empty for a while, and finally the franchise just plain stalled out with its fifth entry, 1969's Gamera vs. Guiron, where we hit the point of complete unwatchability. It's not that much of anything has changed: for enormous swaths of its running time, Gamera vs. Guiron functions almost as a straight remake of the previous year's Gamera vs. Viras, made by most of the same creative team, including director Yuasa Noriaki and screenwriter Takahashi Nisan. Though one man who didn't come back from that film was composer Hirose Kenjiro, replaced in scoring duties by Kikuchi Shunsuke (his first Gamera picture, but not his last - he scored all the remaining first-wave films in the franchise). And this confirms my suspicion that Gamera vs. Viras only turned out to be as fun as it was thanks to Hirose's unexpected, jazzy surf-rock score, adding just the right touch of "...wait, what?" to an otherwise junky kiddie monster movie. Oh, sure, the most salient contribution he made to the series is back, the rousing march "Tsuyoi-zo Gamera" with an all-boy choir spouting their nonsensical praise of the turtle savior of humanity and humanity's children. It shows up twice, no less! But there's a lot of movie beyond that, and it is slow-burning death. Not even one of the most shockingly daft monster designs in the entire history of the daikaiju eiga can turn Gamera vs. Guiron into anything pleasant to watch. I consider myself a purist about watching subtitled foreign-language films versus dubbed ones, but in this case, I think the morbidly curious would be better off watching American producer Sandy Frank's VHS dub from the '80s; at least that's so outlandishly incompetent that it's funny.

But fool that I am, I watched the Japanese original for this review, an in that version we open with a gambit taken right out of the '50s American sci-fi cliché grab bag, Over blurry still photos of nebulae and galactic objects, a stentorian narrator (is there any other kind, in cheap monster movies?) spouts some kind of portentous nonsense about the unknowability of the universe, and the discovery of a new wave from space. "WAVES FROM SPACE" bellows the newspaper headline, in a shot taken right out of the '30s American cliché grab bag. And this wave is quite exciting to everyone, leading Dr. Shiga (Funakoshi Eiji) to hold a press conference to find out what it is.

Dr. Shiga, however, matters not one whit to the rest of the movie, since we have a cluster of young people who already know what's up. Japanese boy Akio (Kajima Nobuhiro), his American friend Tom (Christopher Murphy) - there's bound to be some fascinating sociology explaining why these movies made for an audience of Japanese children suddenly found it very important to have American co-leads for their juvenile heroes, but I am afraid I can't even guess what it might be - and Akio's little sister Tomoko (Akiyama Miyuki), are a trio of space nuts, and they're well aware that it has to be aliens. Akio and Tomoko's mother (Hamada Yuko) is rather down on this, but not enough to prevent the children from going off and doing whatever silly nonsense they like, which involves biking to what proves to be the landing site of a small spaceship. Over Tomoko's objections, the boys scramble in, and are immediately whisked away, almost dying in a collision with a meteor, saved only because Gamera suddenly flies in to bounce the debris from their path. Because Gamera is not merely friend to all children, apparently he stalks them as well.

The craft lands on the planet Terra, which is on Earth's exact orbit but precisely on the opposite side of the sun, so we've never been able to see it. We don't learn that yet; all we know now is that the boys have landed in wildly unconvincing rear-projection of a ruined city, where a silver Gyaos shows up to attack them (you remember Gyaos, right? The daikaiju vampire from Gamera vs. Gyaos? Because this one is just that, spray-painted silver). The monster triggers the arrival of another creature from beneath a pool outside the biggest building, and though we don't know yet that this is Guiron, we've seen the title, and can guess.

And Guiron? Oh, he's a pip. Basically a quadrupedal hammerhead shark with an enormous blade extending straight out from his body instead of the hammer. And with enormous, disconcertingly expressive cow eyes. His fight with the Gyaos is easily the film's highlight, the only action sequence in the whole thing that's remotely well-edited, and astonishingly violent, to boot: Guiron uses his giant knife-nose to reflect the Gyaos's sonic beams and slice limbs off the space bat, one at a time, ending with its head. This gives us a good chance to see that Gyaoses apparently have uniform purple interiors with neither a skeletal structure nor organs.

Guiron returns to his pen after beating this enemy, and the boys are warped into the control room of, apparently, the last two Terrans: a pair of evil Space Babes called Florbella (Kasahara Reiko) and Barbella (Kai Hiroko). Not that they seem evil at first; they're actually quite plaintive in explaining to the boys the history and doomed fate of Terra, overrun by space monsters and running out of energy, with only Guiron to protect it. This may or may not be true, but it's a blind, anyway: what they women really want is to eat the boys' brains, and to do this they lull them into a stupor and scan their memories. Yes, this means stock footage of the previous Gamera films. And having learned that all the children of Earth are protected by a giant turtle guardian, the Terrans are prepared for a fight, and when Gamera arrives to fight Guiron, he is shortly bested and dropped, bleeding and near death, to the bottom of the sea.

To this point, Gamera vs. Guiron has merely been bad; from the start of Gamera vs. Guiron, Rd. 1, it becomes actively unpleasant and never ceases. The fight is a colossal misfire, edited with an eye towards making things as complicated as possible (the physical relationship between the two kaiju is at times literally indecipherable, and staged clumsily between two rather unwieldy fighters - Gamera is played, often as not, by a rigid model that's just kind of swung into Guiron. And once it's over, the film's plot just fucking stops, with scenes that meander around, and cutaways back to Earth, where the boys' mothers are hugely unconcerned with their sons' disappearance, and no clear sense of what, exactly the Terrans are planning to do besides eat two random Earth children. The second monster fight is at least moderately better than the first, owing mostly to how much sillier it is (like the raptor scene in The Lost World: Jurassic Park, it involves using the power of gymnastics to save the day), but it's still not "good", and the movie needs a lot more to redeem it by that point.

It's just so, so dreadful: the effects work is embarrassingly shoddy, with process shots that look so bad, it's almost easier to assume the characters are watching a low-resolution TV monitor than looking through a window at the monsters, and a Gamera who spends most of the movie looking like a big toy. The score - again, the primary reason that Gamera vs. Viras turned out halfway decent, despite sharing all of this film's flaws and compounding two of them (it had a much worse American boy actor, and far more stock footage) - is particularly terrible, bogged down in frothy, frivolous "happy kids! yay!" noodling around for much of the film. The adult actors are all irritating, though how much of that is the performance and how much is the writing, I cannot say. Certainly, Omura Kon, playing the local goofy cop Officer Kondo, target of the kids' mockery, could never redeem his role, and playing it as the Japanese Don Knotts is probably the best he could manage to do.

The movie is boring and ugly, but neither of these are as devastating as how insipid it is: the worst kind of children's entertainment, in which everything is pitched at a goofy, jolly level that prohibits any real sense of drama, and the kid protagonists are idealised to ridiculous lengths. Such as an endless scene in which they discuss the ins and outs of supersonic travel, showing off their incredible knowledge and strangling the movie to death with unwonted fury. It's all very silly, but not the fun kind of silly, not the energetic kind; it's the silly that happens when you've made five Gamera films in five years, and you begin to hold them in a kind of tangible, toxic contempt.