Gamera vs. Guiron (1969)

After news reports of strange transmissions being received from space, friends Akio and Tom observe through their telescope a spaceship that descends into a nearby field. They attempt to go to see it but are promptly returned to bed by Akio's mother. The following morning, with Akio's little sister Tomoko in tow, they ride out to the field on their bicycles to investigate. On their way, they are stopped by Officer Kondo, who warns them not to get into any trouble or he will shave their heads.

Tomoko discovers the spaceship in the vacant lot where they play. Finding it unoccupied, Akio and Tom climb aboard. They playfully press several switches, accidentally launching the ship and themselves into space. Beyond the Earth's atmosphere, Gamera flies alongside the ship in an attempt to save the two children, but he cannot keep up with the alien craft. It speeds off into the far reaches of the solar system.

Some time later, the boys awaken to find the ship crash-landed on an unknown habitable planet, housing an apparently advanced civilization. Departing the craft to investigate the mysterious world, the boys immediately witness a Space Gyaos attacking the nearby colony. They take cover and observe an immense knife-headed monster emerge, quickly cutting the Space Gyaos to pieces. The monster carefully dissects its opponent before returning to its lair under a nearby river.

The boys enter one of the alien buildings, itself part of an enormous complex. In the control room they meet two alien women who identify themselves as Barbella and Florbella. The women explain that the planet, Terra, lies on Earth's orbit directly opposite the sun and that their civilization had prospered for many years until a malfunctioning computer brought calamity upon them, causing flocks of Space Gyaos to overrun the city. From the control center they command their monster Guiron to protect themselves. The other Terrans, they explain, had left the planet to find another inhabitable world, only to meet an unfortunate end. The two women, the last of their race, had called out into space for help -the source of the mysterious radio signals- and had sent the ship to Earth hoping other beings would return to Terra to help. Tom and Akio agree to help the women repair the ship and return to Earth.

On Earth, Tomoko attempts to inform her mother, Tom's mother, and Officer Kondo of the fate of the boys. The two mothers believe it to be a trick the boys are playing so that Tom can stay with Akio. Kondo, however, believes Tomoko's story and tries his best to help despite everyone else's assumption that he merely humors her.

Unbeknownst to the boys, Florbella and Barbella plot to escape to Earth themselves in their repaired two-man craft. To better prepare themselves for Earth, they intend to consume the boys' combined knowledge by eating their brains. They hypnotize the boys and shave Akio's head but are interrupted by the appearance of Gamera in the city. The women sic Guiron on him while they hurry to repair the ship. Gamera battles Guiron fiercely but is badly wounded and left for dead belly-up at the bottom of a lake. The boys come to but are once again captured by the Terran women. This time imprisoned in the control room, they use Tom's toy dart gun to escape their cage, in the process unintentionally pressing other control switches. The Terran women make their escape but Guiron, having been loosed by the boys, cuts the escaping ship in two. Barbella is wounded in the crash. Florbella mercilessly kills her before returning to the relative safety of the Terran complex.

Gamera is roused from the lake and resumes his battle with Guiron. The Terran watchdog gains an advantage by shooting shuriken into Gamera's limbs. It turns towards the control center, having sighted the boys. Frantically trying to defend themselves, Akio and Tom launch a couple of guided missiles: one slams into a far-off building, killing Florbella, while the other is intercepted by Gamera, who hurls it through the shuriken port on Guiron's head. Gamera blasts Guiron, detonating the explosive and killing the enemy monster. He then uses his flame to weld the Terran UFO back together. The boys board the ship, which Gamera carries to Earth in his mouth. Back in the vacant lot where the ship had earlier landed, Tom and Akio are welcomed home by their parents, the media, Tomoko, and Officer Kondo. Akio shares with them his revelation that, while he wanted a world free of war and traffic accidents, such a place did not exist, and that humanity would have to work together to make Earth a better place. Gamera flies away as the three children thank him for his help.