| Director | Koji Shima, Shima Kōji |
|---|
A small ship travels to a rotating space station. Aboard the station, a group of starfish-like aliens called Pairans discuss how to warn humans of an impending disaster, deciding on contacting Japanese scientist Dr. Komura. Meanwhile, flying saucers are spotted over the skies of Tokyo, baffling scientists. A journalist tries to get a statement from Dr. Komura about the sightings, but Komura replies that there is not enough evidence to formulate a hypothesis. At an observatory, Professor Isobe spots an object in his telescope apparently releasing smaller objects.
Isobe discusses his findings with Kumara and a physician, Dr. Matsuda, who believes they should get photographs via a rocket. The photographs they retrieve, however, turn out to be unclear, though they deduce the object has a high energy output. In the meantime, the extraterrestrials have been unsuccessfully attempting to contact humans. They begin appearing in lakes and rivers, frightening local fishermen and sailors. One of the aliens manages to secure a photo of Hikari Aozora, a famous Japanese entertainer. Their plan is for one of the aliens to mutate into the form of Aozora. Back aboard the space station, one of the Pairan leaders, Ginko, volunteers herself. Her starfish form is slowly mutated into a human form.
On Earth, Toru, Isobe's son, discovers the disguised alien floating in the water. After her rescue, Ginko exhibits superhuman characteristics such as jumping ten feet into the air and being able to materialize in different places without needing to walk. Soon, she disrupts Dr. Matsuda's work on a nuclear device, explaining she understands the complex equations he was writing and warning against the effects of a device, leading him to believe she is not human. Shortly afterwards, as the team of scientists discuss her abnormal traits, the camouflaged Ginko appears and reveals her true identity, explaining she is from Paira, a world on the same orbit as Earth but on the opposite side of the Sun. She then continues to reveal her mission, to warn Earth of an imminent collision of a rogue planet, which is dubbed "Planet R" by the media. They send a formal letter to the World Congress, which treats their communication with silent contempt (Japanese: mokusatsu). It takes Planet R's acceleration towards Earth being viewed through the observatory telescope for the World Congress to act. Believing that humanity could resolve the crisis on its own, every nuclear-capable nation on Earth launches its nuclear weapons at the rogue planet, which ineffectively explode on its surface.
In the meantime, a group of spies have abducted Matsuda and are attempting to steal his formula to the nuclear device. Matsuda does not comply and is eventually tied to a chair in a remote building. Planet R begins its closest approach to Earth and begins to wreak havoc, first by causing the atmosphere's temperature to rise to dangerous levels. Following the disruption to the climate, powerful tidal interactions between Earth and Planet R trigger massive earthquakes, followed by tsunamis which inundate coastal areas of Japan. As Earth's destruction approaches, Ginko returns to find that Planet R has not been destroyed. She locates Matsuda through Pairan technology and gathers the formula for the nuclear device, returning to the space station to load the completed weapon into a missile. As the scientists watch, the Pairans fire the missile, which impacts and destroys Planet R, buffeting the Earth with a shock wave, but saving it from total destruction. As the climate returns to normal, Ginko changes back to her original form aboard the space station.