In 1954, after the Japanese freighter Eiko-maru is destroyed near Odo Island, another ship the Bingo-maru is sent to investigate, only to meet the same fate with few survivors. A fishing boat from Odo is also destroyed, with one survivor. Fishing catches mysteriously drop to zero, blamed by an elder on the ancient sea creature known as "Godzilla". Reporters arrive on Odo Island to further investigate. A villager tells one of the reporters that something in the sea is ruining the fishing. That evening, a storm strikes the island, destroying the reporters' helicopter, and Godzilla, briefly seen, destroys 17 homes, kills nine people, and kills 20 of the villagers' livestock.
Odo residents travel to Tokyo to demand disaster relief. The villagers' and reporters' evidence describes damage consistent with something large crushing the village. The government sends paleontologist Kyohei Yamane to investigate the island, where giant radioactive footprints and a trilobite are discovered. The village alarm bell is rung, and Yamane and the villagers rush to see the monster, retreating after seeing it is a giant dinosaur. Yamane presents his findings in Tokyo, estimating that Godzilla has evolved from an ancient sea creature, becoming a terrestrial creature. He concludes that Godzilla has been disturbed by underwater hydrogen bomb testing. Debate ensues about notifying the public about the danger of the monster.
Ten frigates are dispatched to attempt to kill the monster using depth charges. The mission disappoints Yamane, who wants Godzilla to be studied. When Godzilla survives the attack, officials appeal to Yamane for ideas on how to kill the monster. Still, Yamane tells them that Godzilla is unkillable, having survived H-bomb testing, and that it must be studied. When a reporter arrives and asks to interview Serizawa, Emiko escorts the reporter to Serizawa's home. After Serizawa refuses to divulge his current work to the reporter, he gives Emiko a demonstration of his recent project on the condition that she must keep it a secret. The demonstration horrifies her, and she leaves without mentioning the engagement. Shortly after she returns home, Godzilla surfaces from Tokyo Bay and attacks Shinagawa. After attacking a passing train, Godzilla returns to the ocean.
After consulting international experts, the Japan Self-Defense Forces constructs a 50,000 volt electrified fence along the coast and deploys forces to kill Godzilla. Dismayed that there is no plan to study Godzilla for its resistance to radiation, Yamane returns home, where Emiko and Ogata await, hoping to get his consent for them to wed. When Ogata disagrees with Yamane, arguing that Godzilla's threat outweighs any potential benefits from studying the monster, Yamane tells him to leave. Godzilla resurfaces and breaks through the fence to Tokyo with its atomic breath, unleashing more destruction across the city. Further attempts to kill the monster fail, and Godzilla returns to the ocean. The day after, hospitals and shelters are crowded with the maimed and the dead, with some survivors suffering from radiation sickness.
Distraught by the devastation, Emiko tells Ogata about Serizawa's research, a weapon called the "Oxygen Destroyer", which disintegrates oxygen atoms and causes organisms to asphyxiate, then dissolve, leaving nothing behind. Emiko and Ogata go to Serizawa to convince him to use the Oxygen Destroyer. Still, he initially refuses, but after watching a program displaying the nation's current tragedy, Serizawa finally accepts their pleas. As Serizawa burns his notes, Emiko breaks down crying.
A navy ship takes Ogata and Serizawa to plant the device in Tokyo Bay. After finding Godzilla, Serizawa activates the device and cuts off his air supply, taking the secret of the Oxygen Destroyer to his grave. The Oxygen Destroyer successfully kills Godzilla and disintegrates its body. Yamane believes that if nuclear weapons testing continues, another Godzilla may rise in the future.
In 1955, a pilot named Shoichi Tsukioka, who is working for Kaiyo Fishing, Inc., guides a fishing trawler towards a school of bonito. Koji Kobayashi, another pilot, faces engine troubles and makes an emergency landing on Iwato Island. Tsukioka is sent to rescue Kobayashi, but they both encounter two giant dinosaurian creatures locked in battle: Godzilla and a new quadruped monster. The pilots escape as the monsters tumble into the sea.
Tsukioka and Kobayashi go to Osaka to help Dr. Yamane and the authorities investigate the encounter. The new monster is identified as an Ankylosaurus-like carnivore named Anguirus. Dr. Yamane shows the authorities footage of the first Godzilla attack and notes that the first Godzilla was killed by the Oxygen Destroyer, but its inventor died, and that there are no proven countermeasures left against Godzilla. Dr. Yamane suggests issuing a blackout and using drop flares to lure Godzilla away due to the first Godzilla being sensitive to light.
Tsukioka’s girlfriend Hidemi, a plane dispatcher for the fishing company, expresses her concern for Osaka to him, and he reveals that he thought about her when he thought he might die on Iwato Island. They watch as the Japan Air Self-Defense Force (JASDF) take off to find Godzilla, but scientists note that it may prove difficult due to the possibility of Godzilla hiding in caves within the seabed. Later, Godzilla is spotted heading for the Kii Channel between Shikoku and Wakayama Prefecture. Yamaji, Tsukioka’s boss and Hidemi’s father, notes that if Godzilla wreaks havoc in those waters, their fishing company will lose valuable fishing ground and strike a blow at production.
Later, an alert is issued for the Osaka region as Godzilla changes course for Osaka Bay. The Japan Self-Defense Forces (JSDF) cut off the lights in the city and lure Godzilla with flares. Tsukioka leaves Hidemi at her home for safety and leaves with Kobayashi to meet Yamaji at his cannery. Convicts escape from their transport and lead police on a chase that ends with a few convicts crashing into an oil refinery, triggering an explosion, while other convicts escape into Osaka. The explosion lures Godzilla back to Osaka, forcing the JSDF to attack it. Attracted by the flares, Anguirus emerges and engages Godzilla. The monsters battle throughout the city, destroying Yamaji’s cannery and killing the convicts in the process. Godzilla kills Anguirus and returns to the sea after burning the body with its atomic breath.
In the aftermath, Yamaji moves operations to Hokkaido to make full use of the fisheries and cannery, and also sends Kobayashi to guide trawlers. During a company dinner, Tsukioka reunites with Tajima, a friend from college, and the war. Kobayashi hints to Hidemi that he’s fallen in love with a certain woman. The dinner is interrupted by news that a ship was sunk by Godzilla. The following morning, Tsukioka helps the JASDF search for Godzilla and tracks its location on Kamiko Island. Kobayashi departs to aide Tsukioka but leaves his notebook behind. Hidemi peeks at the notebook and discovers a picture of her inside.
Kobayashi attempts to stop Godzilla from escaping but is struck by Godzilla’s atomic breath and crashes into the mountaintop, killing him. The crash creates a small avalanche that engulfs Godzilla, inspiring the JASDF to bury it with a bigger avalanche. Because they lack firepower, the JASDF return to base to reload missiles and Tajima reluctantly accepts Tsukioka’s request to take him. The JSDF creates a wall of fire on the island with barrels full of combustibles to block Godzilla’s escape, while the JASDF triggers avalanches by blasting the mountaintops. Godzilla exhales one last atomic breath before being completely buried by the last avalanche triggered by Tsukioka, the final surviving pilot. Relieved, Tsukioka lets Kobayashi's spirit know that they have finally defeated Godzilla.
Mr. Tako, head of Pacific Pharmaceuticals, is frustrated with the television shows his company is sponsoring and wants something to boost his ratings. When a doctor tells Tako about a giant monster he discovered on the small Faro Island, Tako believes that it would be a brilliant idea to use the monster to gain publicity. Tako sends two men, Osamu Sakurai and Kinsaburo Furue, to find and bring back the monster. Meanwhile, the American nuclear submarine Seahawk gets caught in an iceberg. The iceberg collapses, unleashing Godzilla, who had been trapped within it since 1955.[note 2] Godzilla destroys the submarine and makes its way towards Japan, attacking a military base as it journeys southward.
On Faro Island, a gigantic octopus crawls ashore and attacks the native village in search of Farolacton juice, taken from a species of red berry native to the island. The mysterious Faro monster, revealed to be King Kong, arrives and defeats the octopus. Kong drinks several vases full of the juice while the islanders perform a ceremony, which causes him to fall asleep. Sakurai and Furue place Kong on a large raft and begin to transport him back to Japan. Mr. Tako arrives on the ship transporting Kong, but a JSDF ship stops them and orders that Kong must be kept out of Japan. Meanwhile, Godzilla arrives in Japan and terrorizes the countryside. Kong wakes up and breaks free from the raft. Reaching the mainland, Kong confronts Godzilla and proceeds to throw giant rocks at him. Godzilla is not fazed by King Kong's rock attack and uses its heat ray to burn him. Kong retreats after realizing that he is not yet ready to take on Godzilla.
The JSDF digs a large pit laden with explosives and poison gas and lures Godzilla into it, but Godzilla is unharmed. They next string up a barrier of power lines around the city filled with 1,000,000 volts of electricity, which proves effective against Godzilla. Kong approaches Tokyo and tears through the power lines, feeding off the electricity, which seems to make Kong stronger. Kong then enters Tokyo and captures Fumiko, Sakurai's sister, taking her to the National Diet Building which he then scales. The JSDF launches capsules full of vaporised Farolacton juice, which puts Kong to sleep, and rescue Fumiko. The JSDF decides to transport Kong via balloons to Godzilla, in hopes that they will kill each other.
The next morning, Kong is deployed by helicopters next to Godzilla at the summit of Mount Fuji and the two engage in battle. Godzilla initially has the advantage, dazing Kong with a devastating dropkick and repeated tail blows to his head. Godzilla attempts to burn Kong to death by using its atomic breath to set fire to the foliage around Kong's body. A bolt of lightning from thunder clouds strikes Kong, reviving him and charging him up, and the battle resumes. Godzilla and King Kong fight their way down the mountain and into Atami, where the two monsters destroy Atami Castle while trading blows, before falling off a cliff together into Sagami Bay. After a brief underwater battle, only Kong resurfaces from the water, and he swims back toward his home island. There is no sign of Godzilla, but the JSDF speculates that it may have survived.
Kurata Beach is stricken by a typhoon. The following morning, reporter Ichiro Sakai and his photographer Junko Nakanishi find a strange blue-gray object amongst the wreckage. Later, a giant egg is found floating near Nishi Beach in Shizunoura. Professor Miura attempts to investigate the egg, only to be pestered with questions by Sakai. They soon learn that the villagers had sold the egg to businessman Kumayama for exploitation purposes for his firm Happy Enterprises. At a local hotel, Sakai, Junko, and Miura discuss how to legally counter Kumayama's plans, and find him at the lobby. Kumayama meets with his financial backer Jiro Torahata, who reveals his plans to build the Shizunoura Happy Center around the egg. They are visited by the Shobijin, tiny twin fairies, who attempt to convince them to return the egg but have to escape when the businessmen try to capture them. The Shobijin run into Sakai, Junko, and Miura, and reveal to them that the egg belongs to the colossal insect god Mothra, the recent typhoon caused it to wash up on Japanese waters, and destruction will follow when the larva emerges. The trio agree to help them retrieve the egg, and try to plead with Kumayama and Torahata but are met with resistance. The Shobijin eventually return home to Infant Island without the egg.
Later, Sakai writes scathing articles about Happy Enterprises' insensitivity towards the Shobijin. However, the firm dismisses the articles as slander and open the Shizunoura Happy Center to the public. Kumayama is confronted by the villagers for not paying in full for the egg and renting from their land. Torahata agrees to loan Kumayama additional funds in exchange for putting the egg up as collateral. Kumayama reluctantly accepts and begins incubating the egg. Miura decontaminates Sakai and Junko after examining the object they found in the wreckage and determining it to be highly radioactive. The trio return to Kurata beach to investigate further, but the giant reptilian monster Godzilla emerges from the buried mud, revealing the object to be one of its scales. Citizens evacuate as Godzilla wreaks havoc on Yokkaichi and Nagoya. The Japan Self-Defense Forces (JSDF) are deployed to lead Godzilla to the coast to minimize casualties.
At the suggestion of a colleague, the trio travel to Infant Island to appeal to the Shobijin for Mothra's help. When they arrive, they are horrified by the desolation left behind by past nuclear tests. They are captured by the natives and reveal their intentions to ask for Mothra's help against Godzilla. The Shobijin and natives refuse, seeing it as divine retribution on outsiders for ravaging their island with nuclear tests, and not returning the egg. Junko and Sakai plead that the innocent are also in danger, that they have no right to decide who deserves to live or die, and that civilization is flawed, but is trying hard to make the world better. Mothra agrees to help, but the Shobijin warn that she is on her deathbed.
Back in Japan, the JSDF launch multiple campaigns against Godzilla but to no avail. After losing his fortune, Kumayama confronts Torahata at his hotel, attacks him, and steals his secret funds. Torahata shoots Kumayama, and attempts to escape with the money, but is crushed to death as Godzilla destroys the hotel. Godzilla reaches Nishi Beach, and prepares to destroy the egg until Mothra intervenes and engages Godzilla in battle. Mothra initially gets the upper hand, but is defeated by Godzilla's atomic breath. Mothra uses her last strength to fly to the egg and die next to it.
As the JSDF resume their attacks on Godzilla, the trio and the Shobijin remain with the egg as the twins attempt to make the egg hatch more quickly via musical incantations. On Infant Island, the natives join in a ritual dance, in response to the twins' music. Twin larvae emerge from the egg and follow Godzilla to Iwa island. As the monsters battle, the trio join a rescue party to retrieve students and their teacher left behind on Iwa Island. Godzilla is entrapped by the larvas' silk, tumbles into the sea and sinks. The students and teacher are returned to safety, and the larvae and Shobijin return to Infant Island. Sakai asserts that humanity will thank them by building a better world.
Reporter Naoko Shindo attends a communications session with the UFO society for her television program. However, it is deemed a failure due to Naoko's skepticism. A meteor shower soon descends on Japan, with the largest meteor crashing on Mount Kurodake. Naoko's brother, Detective Shindo, is assigned to guard Princess Salno of Selgina from a political assassination during an unannounced visit to Japan. En route to Japan, an alien entity leads Salno to jump from her plane before it explodes. Professor Miura leads a research team to Mt. Kurodake to investigate the large meteor, where they discover it randomly emitting magnetic waves. Naoko is sent to investigate a prophetess claiming to be from Venus, who predicts that the Pteranodon-like creature, Rodan will emerge from Mount Aso.
The Prophetess catches the attention of both Shindo and Salno's uncle, both of whom recognize her as the supposedly dead Salno. Responsible for the assassination plot, Salno's uncle sends the assassin, Malmess, to kill her. After participating in a TV program, the Shobijin, Mothra's twin fairies, prepare to depart for home but are warned by the Prophetess to not sail. Naoko takes the Prophetess to a hotel to interview her, and discovers that the Shobijin have been following them, heeding the Prophetess' warning before the prehistoric sea monster Godzilla sunk their ship. After confirming that the Prophetess is Salno, Shindo finds her at the hotel and saves her from Malmess. They evacuate after Godzilla and Rodan converge on the city and battle throughout the countryside.
After psychiatrist Dr. Tsukamoto concludes that the Prophetess is human, she predicts the arrival of the alien-dragon King Ghidorah, a monster that destroyed her home on Venus. Miura and his team witness the meteor explode, unleashing the golden three-headed space dragon Ghidorah, who proceeds to attack Matsumoto. The authorities plea with the Shobijin to summon the larva monster Mothra for help, but they warn that Mothra alone could not defeat Ghidorah, and their only hope would be for Godzilla, Rodan, and Mothra to join forces. Under hypnosis, the Prophetess reveals that some Venusians escaped to Earth from Ghidorah and assimilated with humans, but at the cost of losing most of their abilities except prediction.
After Malmess overhears Tsukamoto recommending shock therapy next, he increases the voltage to a fatal degree, but fails after the power lines are destroyed by Godzilla. After thwarting Malmess and his crew, Shindo evacuates to the mountains with the Prophetess, Tsukamoto, Naoko, Miura, and the Shobijin. Mothra attempts to convince Godzilla and Rodan to set aside their differences to save the planet, but both refuse due to years of harassment from humans. However, after seeing Mothra attempt to battle Ghidorah on her own, Godzilla and Rodan change their minds and rush to her aid. The Prophetess wanders off and regains her memories after Malmess nearly kills her. Shindo manages to protect her just in time and Malmess falls to his death. The monsters overwhelm Ghidorah and force it to flee into outer space. Prior to departing for home, Princess Salno reveals to Shindo that she has no memory as the Prophetess, but remembers the three events when Shindo saved her, and thanks him and Naoko for their help. Godzilla and Rodan watch as Mothra journeys back home with the Shobijin, who bid farewell to all.
In the year 196X,[4] two astronauts, Fuji and Glenn, are sent to investigate the surface of the mysterious "Planet X" recently detected on the far side of Jupiter. There they encounter advanced and seemingly benevolent human-like beings called the Xiliens and their leader, the Controller. The aliens usher the astronauts into their underground base, shortly before the surface is attacked by a creature that the Xiliens call "Monster Zero", but which the astronauts recognize as King Ghidorah, a planet-destroying monster that had attacked Earth once before[c]. The monster eventually leaves, but the Controller states that Ghidorah has been attacking repeatedly, forcing them to live underground in constant fear. He requests to borrow the Earth monsters Godzilla and Rodan to protect Planet X from Ghidorah, in return for the cure for cancer.[d] The astronauts return to Earth and deliver the message.
Meanwhile, an inventor named Tetsuo has designed a personal alarm that emits an ear-splitting electric siren. He sells it to a businesswoman named Namikawa, but she disappears before paying him. Tetsuo is romantically involved with Fuji's sister, Haruno, but Fuji disapproves, finding him unworthy of Haruno. Tetsuo sees Namikawa with Glenn and later follows her, but he is captured and imprisoned by Xilien spies.
Glenn and Fuji begin to worry that the Xiliens may have ulterior motives. Their suspicions appear confirmed when three Xilien spacecraft appear in Japan. The Controller apologizes for coming to Earth without permission. The Xiliens locate Godzilla and Rodan, both sleeping, and use their technology to transport them to Planet X. They also bring Glenn, Fuji, and the scientist Sakurai with them. After a brief confrontation, the Earth monsters succeed in driving Ghidorah away. Glenn and Fuji sneak away during the battle and encounter two Xilien women, both of whom look identical to Namikawa. Xilien guards confront the astronauts and bring them back to the Controller, who reprimands but does not punish them. The astronauts are given a tape with instructions for the miracle cure and sent home, leaving Godzilla and Rodan behind. The tape is played for the world's leaders, but instead, it contains an ultimatum demanding that they surrender Earth to the Xiliens or be destroyed by Godzilla, Rodan, and Ghidorah, who are all under the aliens' mental control.
Glenn storms into Namikawa's office and finds her in Xilien garb. She admits that she is one of their spies, but confesses that she has fallen in love with him. Her commander arrives to arrest Glenn and executes Namikawa for letting emotion cloud her judgment, but not before she slips a note into Glenn's pocket. Glenn is taken to the same cell as Tetsuo. They read Namikawa's note, which explains that the sound from Tetsuo's invention disrupts the Xiliens' electronics. Tetsuo has a prototype with him, which he activates, weakening their captors and allowing them to escape.
Sakurai and Fuji build a device to disrupt the Xiliens' control over the monsters. Glenn and Tetsuo arrive to share the Xiliens' weakness. As the monsters attack, Sakurai's device is activated and the sound from Tetsuo's alarm is broadcast over the radio. The invasion is thwarted and the Xiliens, unable to fight back or retreat, destroy themselves en masse. The monsters awaken from their trances and a fight ensues. All three topple off a cliff into the ocean; Ghidorah surfaces and flies back into outer space, while those watching speculate that Godzilla and Rodan are probably still alive. Fuji acknowledges Tetsuo's important role in the victory and no longer thinks poorly of him. Sakurai states that he wants to send Glenn and Fuji back to Planet X to study the planet thoroughly.[e] The astronauts are reluctant, but make the best of the moment, happy that Earth is safe.
After Yata is lost at sea, his brother Ryota steals a yacht with his two friends and a bank robber. However, the crew runs afoul of Ebirah, a giant lobster-like creature, and washes ashore on Letchi Island. There, the Red Bamboo, a terrorist organization, manufactures heavy water for selling weapons of mass destruction and a yellow liquid that keeps Ebirah at bay, presumably controlling him. The Red Bamboo has enslaved natives from nearby Infant Island to create the yellow liquid, while the natives hope that Mothra will awaken in her winged, adult form and rescue them.
In their efforts to avoid capture, Ryota and his friends, aided by Daiyo, a native girl, come across Godzilla, who previously fought King Ghidorah and is now sleeping within a cliffside cavern. The group devises a plan to defeat the Red Bamboo and escape the island. In the process, they awaken Godzilla using a makeshift lightning rod. Godzilla fights Ebirah, but the huge crustacean escapes. Godzilla is then attacked by a giant condor and a squadron of Red Bamboo fighter jets. Using its atomic breath, Godzilla destroys the jets and kills the giant bird.
Ryota and his friends retrieve the missing Yata and free the enslaved natives as Godzilla begins to destroy the Red Bamboo's base of operations, smashing a tower that causes a countdown that will destroy the island in a nuclear explosion. Godzilla fights Ebirah and defeats it, ripping its claws off, and forcing it to retreat into the sea. The natives await for Mothra to carry them off in a large net. However, when she gets to the island, Mothra is challenged by Godzilla due to a previous confrontation. Mothra manages to repel Godzilla and save her people and the human heroes. Godzilla also escapes just before the bomb detonates and destroys the island.
The egg hatches, revealing a baby Godzilla named Minilla. The scientists realize that his telepathic cries for help were the cause of the interference that ruined their experiment. Shortly afterwards, Godzilla arrives on the island in response to the infant's cries, and demolishes the scientists' base while rushing to defend the baby. Godzilla kills two of the Kamacuras during the battle while one manages to fly away to safety. Saeko introduces herself to and bonds with the newborn monster, feeding him a mango. Godzilla then returns and adopts Minilla as his son.
Minilla quickly grows to about half the size of his father, and Godzilla begins instructing him on the important monster skills of roaring and using the atomic ray, as Maki and Saeko observe them. At first, Minilla has difficulty producing anything besides atomic smoke rings, but Godzilla discovers that stressful conditions (such as stepping on his tail) or motivation produces a true radioactive blast. Minilla comes to the aid of Saeko when she is attacked by a Kamacuras, but he inadvertently awakens Kumonga (Spiga in the English-dubbed version), a giant spider that was sleeping in a valley which Saeko's father witnessed roaming on the island before. Kumonga attacks Saeko's cave where the scientists are hiding and Minilla stumbles into battle.
Kumonga traps Minilla and the final Kamacuras with its webbing, but as Kumonga begins to feed on the deceased Kamacuras, Godzilla arrives. Godzilla saves Minilla and they work together to defeat Kumonga by using their atomic rays to kill it. Hoping to keep the monsters from interfering in their attempt to escape the island, the scientists finally use their perfected weather altering device on the island and the once tropical island becomes buried in snow and ice. As the scientists are saved by an American submarine, Godzilla and Minilla embrace and begin to hibernate as they wait for the island to become tropical again.
At the end of the 20th century[a], all of the Earth's monsters have been collected by the United Nations Science Committee and confined in an area known as Monsterland, located in the Ogasawara island chain. A special control center is constructed underneath the island to ensure that the monsters stay secure and to serve as a research facility to study them.
When communications with Monsterland are suddenly and mysteriously severed, and all of the monsters begin attacking world capitals, Dr. Yoshida of the UNSC orders captain Katsuo Yamabe and the crew of his spaceship, Moonlight SY-3, to investigate Monsterland. There, they discover that the scientists, led by Dr. Otani, have become mind-controlled slaves of a feminine extraterrestrial race identifying themselves as the Kilaaks, who reveal that they are in control of the monsters. Their leader demands that the human race surrender, or face total annihilation.
Godzilla attacks New York City, Rodan invades Moscow, Mothra larva lays waste to Beijing, Gorosaurus destroys Paris[b], and Manda attacks London. The attacks were set in to motion to draw attention away from Japan, so that the Kilaaks can establish an underground stronghold near Mount Fuji. The Kilaaks then turn their next major attack onto Tokyo and, without serious opposition, become arrogant in their aims until the UNSC discover, after recovering the Kilaaks' monster mind-control devices from around the world, that they have switched to broadcasting the control signals from their base under the Moon's surface. In a desperate battle, the crew of the SY-3 destroys the Kilaak's lunar outpost and returns the Kilaak control system to Earth.
With all of the monsters under the control of the UNSC, the Kilaaks call King Ghidorah, who is dispatched to protect the Kilaak stronghold, battling Godzilla, Minilla, Mothra larva, Rodan, Gorosaurus, Anguirus, Kumonga, Baragon and Varan. While seemingly invincible, Ghidorah is eventually overpowered by the combined strength of the Earth monsters and is killed. Refusing to admit defeat, the Kilaaks produce their ace, a burning monster they call the Fire Dragon, which begins to torch Tokyo and destroys the control center on Ogasawara.
Suddenly, Godzilla attacks and destroys the Kilaaks' underground base, revealing that the Earth's monsters instinctively know who their enemies are. Yamabe then pursues the Fire Dragon in the SY-3 and narrowly achieves victory for the human race. The Fire Dragon is revealed to be a flaming Kilaak UFO and is destroyed. With the Kilaaks defeated, Godzilla and the other monsters eventually return to Monsterland to live in peace.
Ichiro Miki is a highly imaginative but lonely latchkey boy growing up in urban and polluted Kawasaki. Every day he comes home to his family's empty apartment. His only friends are a toymaker named Shinpei Minami and a young girl named Sachiko. Every day after school, Ichiro is tormented by a gang of bullies led by a child named Sanko Gabara.
To escape his loneliness, Ichiro sleeps and dreams about visiting Monster Island. During his visit, he witnesses Godzilla battle three Kamacuras —a form of giant mantis— brutally outpowering the three. Ichiro is then chased by a rogue Kamacuras and falls into a deep cave, but luckily avoids being caught by Kamacuras. Shortly afterwards, Ichiro is rescued from the cave by Godzilla's son Minilla. Coincidentally, Ichiro quickly learns that Minilla has bully problems too, as he is bullied by a mutant amphibian monster known as Gabara.
Ichiro is then awoken by Shinpei who informs him that his mother Tamiko must work late again. Ichiro goes out to play, but is then frightened by the bullies and finds and explores an abandoned factory. After finding some souvenirs (tubes, a headset, and a wallet with someone's [necessarily the suspect's] license), Ichiro leaves the factory after hearing some sirens close by. After Ichiro leaves, two bank robbers who were hiding out in the factory learn that Ichiro has found one of their driver's licenses and follow him in order to kidnap him.
Later, after his dinner with Shinpei, Ichiro dreams again and reunites with Minilla. Together they both watch as Godzilla battles other monsters such as Ebirah, Kumonga, Giant Condor and some invading jets. Then in the middle of Godzilla's fights, Gabara appears and Minilla is forced to battle it, and after a short and one-on-one battle, Minilla runs away in fear. Godzilla returns to train Minilla how to fight and use its atomic breath. However, Ichiro is woken up this time by the bank robbers and is taken hostage as a means of protection from the authorities.
Out of fear and being watched by the bank robbers, Ichiro calls for Minilla's help and falls asleep again where he witnesses Minilla being beaten up by Gabara again. Finally, Ichiro helps Minilla fight back at Gabara and eventually, Minilla emerges victorious by catapulting Gabara through the air with a seesaw-like log. Godzilla, who was in the area watching comes to congratulate Minilla for his victory but is ambushed by a vengeful Gabara. Godzilla easily defeats and sends Gabara into retreat, never to bother Minilla again.
Now from his experiences in his dreams, Ichiro learns how to face his fears and fight back, gaining the courage to outwit the bank robbers just in time for the police, called by Shinpei, to arrive and arrest them. The next day, Ichiro stands up to Sanko and his gang and emerges victorious, regaining his pride and confidence in the process. He also gains their friendship when he plays a prank on a billboard painter.
Hedorah, an individual of a species of amorphous extraterrestrial alien from the Horsehead Nebula, is transported to Earth by a comet. Upon arrival, it feeds on Earth's pollutants and grows into a poisonous sea monster with the ability to produce sulfuric acid. After it sinks an oil tanker and attacks Dr. Toru Yano and his young son Ken, scarring the doctor, Hedorah's toxic existence is revealed to the public. Ken has visions of Godzilla fighting the world's pollution and insists Godzilla will come to mankind's aid against Hedorah.
Hedorah metamorphoses into an amphibious form, allowing it to move onto land to feed on additional sources of pollution. As Hedorah makes its way to a power station to consume the smoke from its chimneys, it is confronted by Godzilla. Hedorah is easily overpowered by Godzilla and retreats into the ocean. However, during the fight, several pieces of Hedorah's body are flung off, which then crawl back into the sea to grow anew and allow Hedorah to become even more powerful. It returns shortly afterwards in its flying form, then assuming its full form, which demonstrates some of the strongest powers it has access to yet.
Thousands of people across Japan are killed in Hedorah's raids. As hope fades, a party is thrown on Mount Fuji to celebrate one last day of life before the country—and then, the rest of the world—succumbs to Hedorah's unstoppable power. Ken, Yukio Keuchi, Miki Fujinomiya, and the other partygoers realize that Godzilla and Hedorah have also converged on Mount Fuji for a decisive confrontation. During the battle, Godzilla is quickly outmatched by Hedorah's impressive durability and fearsome strength, losing an eye and sustaining a full thickness chemical burn to a hand - right down to the bone - from contact with Hedorah's acidic body and blood, which corrodes anything that comes into contact with it. Finally, Godzilla is almost killed by Hedorah after the alien throws Godzilla into a pit, then attempts to drown Godzilla with a deluge of chemical sludge.
Dr. Toru and his wife Toshie have determined that drying out Hedorah's body may destroy the otherwise unkillable monster. While Godzilla and Hedorah fought, the JSDF swiftly constructed two gigantic electrodes for this purpose and switch them on in an effort to give Godzilla a chance to escape the pit and return to the fight.
Suddenly, the electrodes short out, the power cut off by Godzilla and Hedorah's violent battle. Godzilla reactivates and energizes the electrodes with its atomic breath, which dehydrates Hedorah's exterior. Hedorah's body splits open, and the alien tries to escape using its flying form, but Godzilla propels itself through the air using its atomic breath as a jet to give chase. Godzilla drags Hedorah back to the electrodes and continues to dehydrate it until Hedorah is on the brink of defeat. Godzilla tears open Hedorah's dried-out body and exposes it to the electrodes again, dehydrating pieces of Hedorah's remains until they disintegrate into dust. Godzilla returns to the ocean, but not before pausing to gaze sternly at the surviving humans. Ken bids farewell to Godzilla.
The Nebulans, a race of cockroach-like aliens from a planet in M Space Hunter Nebula, plot to take over the Earth, as their home planet has been destroyed by pollution from another race native to the planet, which destroyed itself in the process. To carry out their plans in secret, they disguise themselves using skin suits based on deceased humans, and build World Children's Land, a theme park which serves as a disguise for their base of operations, centered inside a statue of Godzilla called the Godzilla Tower. They also have King Ghidorah and Gigan at their disposal, guiding the monsters using Action Signal Tapes, which broadcast a frequency that instructs them on what to do. The aliens plan to use their monsters to wipe out human civilisation.
Gengo Odaka, a freelance manga artist, inadvertently discovers one of the tapes after being hired by the Nebulans to produce concept art for the park. When the tape is played, the signal is heard by Godzilla and Anguirus on Monster Island, who realize something is amiss. Anguirus is sent to Tokyo to investigate, but is driven back by the JSDF. After reporting back to Godzilla, the two monsters set off for Tokyo again to confront the Nebulans at World Children's Land.
As they arrive, the Nebulans send Gigan and Ghidorah into battle, who prove to be more than a match for Godzilla and Anguirus; to make matters worse, Godzilla is badly injured by the Nebulans when the Godzilla Tower fires an extremely powerful laser weapon at Godzilla, and is rapidly overpowered by Gigan's assortment of bladed weapons. However, Gengo and his friends come to the aid of Godzilla and Anguirus when they destroy Godzilla Tower with TNT supplied by the JSDF, killing the Nebulans and leaving Ghidorah and Gigan without instruction.
Though the extraterrestrial monsters manage to regain their composure and briefly resume the fight, Godzilla and Anguirus now have the upper hand, and manage to drive both Ghidorah and Gigan into a full retreat. With the invasion defeated, Godzilla and Anguirus begin the return trip to Monster Island, much to the cheers of the humans who helped them fend off their opponents.
In the first part of 1971, the second of a series of underground nuclear tests is conducted, near the Aleutians, sending shockwaves as far as Monster Island in the South Pacific, severely damaging the island paradise and sending Anguirus plummeting into the depths of the Earth, with Godzilla narrowly escaping the fissure into which its friends tumble.
For millions of years, Seatopia, an opulent undersea civilization that resides in vast cities reminiscent of those of Ancient Greece and Rome, has existed in relative peace, ruled by Emperor Antonio, but nuclear tests in recent years have severely affected the cities via the earthquakes the tests produced. With the Seatopian capital badly affected by the most recent test, the Seatopians plan to unleash their civilization's beetle-styled titan, Megalon, to destroy the surface world out of vengeance.
On the surface, an inventor named Goro Ibuki, his little brother Rokuro, and Goro's friend Hiroshi Jinkawa are relaxing near a lake, when Seatopia makes itself known to the Earth by drying up the lake and using it as a base of operation. As they return home they are ambushed by agents of Seatopia who are trying to steal Jet Jaguar, a humanoid shaped robot under construction by the trio of inventors. However, the agents' first attempt is botched and they are forced to flee to safety.
Some time later, Jet Jaguar is completed but the trio of inventors are knocked unconscious by the returning Seatopian agents. The agents' plan is to use Jet Jaguar to guide Megalon to destroy whatever city Seatopia commands him. Goro and Rokuro are sent to be killed, while Hiroshi is taken hostage. Megalon is finally released to the surface while Jet Jaguar is put under the control of the Seatopians and is used to guide Megalon to attack Tokyo with the JSDF failing to defeat the monster. Eventually, the trio of heroes manage to escape and devise a plan to send Jet Jaguar to get Godzilla's help using Jet Jaguar's secondary control system.
After uniting with Japan's Defense Force, Goro manages to regain control of Jet Jaguar and sends the robot to Monster Island to bring Godzilla to fight Megalon. Without a guide to control its actions, Megalon flails around relentlessly and aimlessly fighting with the Defense Force and destroying the outskirts of Tokyo. The Seatopians learn of Jet Jaguar's turn and thus send out a distress call to their allies, the Nebulans[b] to send Gigan to assist Megalon.
As Godzilla journeys to fight Megalon, Jet Jaguar starts acting on its own and ignoring commands to the surprise of its inventors and grows to gigantic proportions to face Megalon itself until Godzilla arrives. The battle is roughly at a standstill until Gigan arrives and both Megalon and Gigan double team Jet Jaguar. Godzilla finally arrives to assist Jet Jaguar and the odds become even.
After a long and brutal fight, Gigan and Megalon both retreat and Godzilla and Jet Jaguar shake hands on a job well done. Jet Jaguar bids Godzilla farewell and Godzilla returns to Monster Island. Jet Jaguar returns to his human-size form and returns home with Goro and Rokuro.
In Okinawa, an Azumi priestess has a vision of a city being destroyed by a giant monster. Masahiko Shimizu discovers space titanium while spelunking and takes it to Professor Miyajima for examination. An excavation led by Masahiko's brother Keisuke uncovers a chamber filled with ancient artifacts and a mural bearing an ominous prophecy: "When a black mountain appears above the clouds, a huge monster will arise and try to destroy the world; but when the red moon sets and the sun rises in the west, two monsters shall appear to save the people." Keisuke is joined by archaeologist Saeko Kaneshiro, who translates the prophecy and takes a statue bearing the likeness of Okinawa's guardian monster King Caesar to study. Two men stalk them, one claiming to be a reporter while the other attempts to steal the statue.
Following the appearance of a black cloud resembling a mountain, a Godzilla imposter emerges from Mount Fuji and begins a destructive rampage. Godzilla's ally, Anguirus, confronts the imposter, only to be injured and forced to retreat. Keisuke arrives shortly after to check on Masahiko and Miyajima. As the Godzilla imposter's rampage continues, the real Godzilla confronts the imposter, revealed to be Mechagodzilla, a massive mecha with advanced weaponry made of space titanium. Both monsters injure each other and retreat.
Keisuke and Saeko take the statue back to the temple, but are confronted by the thief once again. During the fight, the skin on half of the stranger's face melts away, revealing an ape-like alien from the Third Planet of the Black Hole called Simeon. The Simeon intruder attempts to kill Keisuke, but an unseen gunman kills him before Keisuke and Saeko catch a brief glimpse of the reporter. Godzilla arrives on Monster Island during a thunderstorm and is struck by lightning multiple times, reinvigorating it.
Masahiko, Miyajima and his daughter Ikuko explore the cave where the space titanium was found, but are captured by Simeons, who plan to use Mechagodzilla to conquer Earth. Their commander, Kuronuma, forces Miyajima to repair the mecha. While Saeko checks into a hotel and guards the statue, Keisuke leaves to meet Masahiko at the caves, only to encounter the reporter, who reveals himself as Nanbara, an Interpol agent who has been tracking the Simeons. After Nanbara and Keisuke infiltrate Simeon base and free the prisoners, Keisuke and Ikuko leave to pick up Saeko and the statue while Miyajima, Nanbara, and Masahiko stay behind, only to be recaptured by Kuronuma.
The next morning, a lunar eclipse results in a red moon and a mirage of the sun rising in the west. Seeing this, the team realizes they have to awaken Caesar. They meet with the priestess and her grandfather and place the statue in the temple, revealing Caesar's resting place. As Kuronuma dispatches Mechagodzilla, the priestess sings to awaken Caesar and Godzilla arrives. The two monsters join forces to fight Mechagodzilla. When the mecha tries to escape, Godzilla creates an electromagnetic field to attract Mechagodzilla before tearing off its head, destroying Mechagodzilla. While the Simeons are distracted, Nanbara and the others free themselves, kill their captors, and sabotage the base, fleeing as it explodes. With the enemy defeated, Godzilla heads out to the ocean and Caesar returns to his resting place while the humans rejoice.
Following Mechagodzilla's and the Simeons' defeat by Godzilla and Okinawan guardian monster King Caesar,[a] Interpol agents search for Mechagodzilla's remains at the bottom of the Okinawan Sea in the hopes of gathering information on the Simeons. Their submarine is attacked by a giant marine dinosaur they name Titanosaurus and the crew vanishes.
Interpol launches an investigation into the incident. With the help of marine biologist Akira Ichinose, they trace Titanosaurus to a reclusive mad scientist named Shinzô Mafune, who wants to destroy mankind. While the group visits Mafune's home, they meet his daughter, Katsura, who secretly underwent surgery and became a cyborg after she was injured during one of her father's experiments. Katsura claims her father is dead and that she burned his notes about Titanosaurus. Mafune is visited by Tsuda, an aide to the Simeon supreme leader Mugal, who is leading a project to rebuild Mechagodzilla into Mechagodzilla 2. Mugal offers the Simeons' services to Mafune so that their respective monsters can wipe out mankind. A control device for Mechagodzilla 2 is implanted into Katsura.
Ichinose falls in love with Katsura and unwittingly gives her Interpol's information on the Simeons, Mechagodzilla, and Titanosaurus. An impatient Mafune releases Titanosaurus on Yokosuka without the Simeons' permission. While Interpol discovers Titanosaurus is vulnerable to supersonic waves, Katsura destroys their supersonic wave oscillator. Godzilla arrives and easily defeats Titanosaurus, causing the latter to retreat.
When Ichinose visits Katsura, the Simeons capture him and unleash Mechagodzilla 2 and Titanosaurus on Tokyo. Interpol repairs their wave oscillator and the Japanese armed forces struggle to fend off the monsters. Godzilla arrives but is outmatched until Interpol distracts Titanosaurus with the repaired wave oscillator, allowing Godzilla to focus on Mechagodzilla 2. Interpol agents infiltrate the Simeons' hideout, rescue Ichinose, and kill Mafune and many of the Simeons. The remaining Simeons attempt to escape, but Godzilla shoots down their ships with atomic breath. The wounded Katsura shoots herself to disable Mechagodzilla 2's control device. Godzilla destroys Mechagodzilla 2, but Katsura dies in Ichinose's arms. With help from Interpol, Godzilla defeats Titanosaurus and returns to the ocean.