The climax of the film, which was shot last week in Toho Studios in Tokyo, is a showdown between the two monsters in the southern city of Fukuoka, where both are seeking to harness extra-terrestrial energy sources from crystals that have landed in the city's streets. Who will triumph? Anxious Japanese must hold their breaths until 10 December, when Godzilla v Space Godzilla opens in cinemas.
It is 40 years since Godzilla first hit cinemas in Japan, delighting audiences as he razed familiar landmarks with a flick of his tail or fried them with a blast of the heat ray from his jaws. Over 82 million people have seen the first 20 films, and yet the fascination with the creature who tears apart the symbols of economic development persists.
Born out of fears of radioactivity when memories of the atomic bombing of Hiroshima and Nagasaki were still fresh, and pandering to deeply-held feelings of vulnerability shared by most Japanese, Godzilla has traded on Japan's dreams and nightmares for four decades. His biography is ambivalent. Sometimes protecting Japan against foreign - ie American - enemies, sometimes representing the threat himself, Godzilla has served as Japan's bad conscience about itself. And no matter how many times he is defeated, buried or hurled back into the sea he always returns.
'The popularity of Godzilla indicates our unconscious revolt against the superficial peace and economic development of Japan,' said Toshio Takahashi, a lecturer in literature at Tokyo's Waseda University, and author of At Night Godzilla Comes. 'Audiences are thrilled when Godzilla destroys the rapid but shallow aspects of modernisation.'
The film-makers always seek permission to model and destroy a city or a monument in their film - and there is a waiting list of willing candidates. The city of Fukuoka on the southern Japanese island of Kyushu mounted a campaign to feature in the current film, since the monster had never destroyed anything on Kyushu.
The first Godzilla film was made in 1954, the year that a Japanese fishing boat was showered by radioactive fallout from a US hydrogen bomb test on the Bikini atoll in the Pacific. In the film the monster, a Tyrannosaurus Rex that mutates under the influence of radioactivity, comes to Japan and destroys one city after another before returning to the sea. Since then a central theme of all the Godzilla films has been a strong anti-nuclear message. The name 'Godzilla', pronounced 'Gojira' in Japanese, is a compound of the word gorilla and kujira (whale).
The single most popular film was King Kong v Godzilla, released in 1962, which attracted a total audience of 12.5 million people with its conflict between Eastern and Western monster types. After that the producers dreamed up one new monster after another to take on Godzilla. The ever more exotic parade of giant moths, hydra-headed lizards and gleaming steel robo-monsters came to resemble the theatrical aspects of professional tag wrestling, whose very improbability and over-acted posturing is part of the fun.
Nor has Toho Co Ltd - Japan's largest film-maker, which has made all the Godzilla films - tried to improve on the matchbox sets and old-fashioned special effects. In Number 9 Studio last week an actor wearing the 90 kg Godzilla suit stood patiently in the middle of a one fiftieth scale model of Fukuoka waiting to be hit by a crystal missile. The missile was attached to piano wire, and off camera stage-hands ran the length of the hall pulling the wire until the missile hit the monster's chest. Not for Godzilla the sophisticated electronic special effects of Hollywood blockbusters.
'We do that on purpose,' said Koichi Kawakita, the special effects director of Godzilla v Space Godzilla. 'It adds to the charm.' The budget is also of un-Hollywood proportions: a mere pounds 6.5m for the entire film.
Each film takes on some social issue of the time: the new one is to tackle conservation of the environment. In the early films, the fear of nuclear weapons and holocaust was pronounced. In the 1984 Return of Godzilla the Japanese Prime Minister turns down a US and Soviet request to use nuclear weapons against the monster. At the height of domestic political scandals, the 1992 Godzilla v The Thing saw the larva of the giant moth spinning a cocoon around the country's parliament building, literally tying up Japan's political establishment.
Some films have been controversial: in the 1991 Godzilla v King Ghidorah, the monster is fighting a plot by the US to make Japan open its markets. In a time-leap Godzilla helps Japanese troops defeat US Marines in the Pacific in 1944.
And each film has given a positive role to the controversial Japanese armed forces, which were disbanded after the last war. To rebuild trust among the populace the armed forces have concentrated on disaster relief for floods, typhoons and earthquakes, and such a role fits in well to the Godzilla films. The troops are allowed to use their most modern weapons against Godzilla, in the name of protecting Japan. So grateful is the military for the positive publicity it gets from the Godzilla films that all personnel perform for free.
But for most Japanese, the most thrilling aspect of Godzilla films is the freedom to destroy the cluttered constrictions of modern urban life, like a child building a sandcastle who enjoys knocking it down again. 'Godzilla is scary but charming,' said Shogo Tomiyama, the producer of the latest film. 'He is a mixture of dream and nightmare, that we can find in the mind of a child.'