Godzilla vs. Hedorah (1971)

Young Ken Yano is playing outside with his Godzilla toys when his uncle Yukio Keuchi asks him if Godzilla is his favorite. Ken responds that to him, Godzilla is Superman. Local fisherman Gohei comes to the Yanos' home to show Ken's biologist father Toru a strange black tadpole he found. Dr. Yano is unable to identify the specimen and asks where Gohei caught it. Gohei responds that he caught it in Suruga Bay, which is becoming more polluted by the day. Later, while watching the news, the family sees a report about an accident at Suruga Bay where a huge black monster attacked two oil tankers that had crashed. Ken immediately recognizes the monster as a larger version of the tadpole Gohei had brought over. Dr. Yano decides to investigate and dons a diving suit to explore Suruga Bay. Ken stays behind on the rocks to wait for his father. As Yano dives beneath Suruga Bay, he finds the seafloor polluted with all manner of garbage and even several dead waterfowl. While waiting for his father, Ken sees the huge monster tadpole from the television approaching him. The creature leaps from the water, with Ken defending himself with a knife. The knife slices harmlessly through the monster, which lands back in the water and swims toward Yano's location. Ken notices he is otherwise unharmed save for a burn on his hand, and calls out for his father, and tells him he saw the monster. Beneath the surface, Yano sees the monster tadpole approaching and hides. He is however unable to escape the creature, which attacks him.

Following the attack, Dr. Yano is confined to bed rest with gruesome burns on his face. Reporters interview him and Ken about their encounter with the monster, which Ken has named Hedorah. Ken tells the reporters that Hedorah comes from the sludge dumped into the sea and feeds on pollution. Furthermore, he says there is more than just one Hedorah. Yano agrees with what his son has said, adding that the Hedorah they encountered was dangerous enough to severely burn his face. The reporters prepare to take pictures of Yano's injuries, but his wife Toshie asks them not to. Yano says he wants people to see pictures of him so they know how severe the threat is, and asks the reporters to take photos. Ken shows the reporters his hand, saying Hedorah got him too. Over the following days, numerous accidents occur involving tankers, all caused by the monster dubbed Hedorah. Ken has a dream where Godzilla arises to battle Hedorah in response to the severe pollution of the sea. He heads to his father's laboratory to tell his parents about his dream. Inside the lab, Dr. Yano finds that the Hedorah Gohei brought him has dried out and begun to crumble. He is shocked to find that the so-called tadpole is actually a mineral. He places powder from the Hedorah in water, where it forms into very small Hedorahs. He notices that when he places them in dirty water, they will combine into a larger Hedorah. He says this proves Ken's theory that Hedorah comes to life in polluted waters.

Yukio attends a nightclub where his girlfriend Miki Fujinomiya is performing. For a brief moment, he hallucinates that all of the patrons have fish heads. Not far from the club, Hedorah evolves into a terrestrial Landing Stage and crawls onto land in a port area. The Smog Monster approaches a nearby factory and places its head over the smokestack, breathing in the toxic pollutants and growing. The creature's feeding is interrupted when it overhears Godzilla's roar. Hedorah responds to the call with its own roar and watches as Godzilla approaches. Hedorah leaps at Godzilla, who manages to tear himself free of the monster's grip. Godzilla grabs Hedorah and swings it through the air, causing a chunk of its body to crash into the upstairs of the nightclub. Yukio, Miki, and all of the patrons then witness the fragment of Hedorah slither down the stairs before retreating up, leaving a sludge-covered cat in its wake. Yukio and Miki escape to Yukio's car, from which they see Godzilla pursuing Hedorah. The monsters exchange taunts, with Hedorah seemingly mocking Godzilla's own gestures. They begin to fight again as Hedorah leaps at Godzilla but misses. Godzilla fires his atomic breath at Hedorah when it is on the ground, but this only causes his enemy to spark. Hedorah quickly retreats into the ocean, with Godzilla in hot pursuit. Godzilla fires his atomic breath in the water, trying to hit Hedorah, but to no avail.

In the aftermath of the battle, Yukio takes Dr. Yano to the area in the port where he saw Hedorah spark. Yano asks his family to harvest as many samples of ash in the area that they can find. Back in his lab, Yano has uncovered the secret to Hedorah's biology. The creature is composed of an undiscovered element he calls Hedrium, which absorbs toxins and pollutants and converts them into energy for Hedorah. Thus, Hedorah literally feeds on manmade pollution. Miki asks if this would solve their pollution problem, but Yano responds that it would make things far worse. When Hedrium reacts with pollutants, it produces sulfuric acid, the same acid which caused the burns on his face. When it feeds on pollutants, Hedorah produces a deadly sulfuric smog which corroded metal in the area where it came ashore. While it absorbs manmade pollutants, Hedorah creates its own toxic smog that is far more deadly. Yano believes Hedorah is an alien which came to Earth on a comet, likely originating from a dark, sticky planet somewhere far away from Earth. Miki and Yukio take Ken to an amusement park on a bright and sunny day, when it is believed Hedorah won't come ashore. Ken sees Godzilla in the distance while he is on a rollercoaster and quickly gets off once the ride stops and runs off to call his father. He calls his father from a phone booth and says that if Godzilla is here, Hedorah must be as well. Yano tells his son to go to his mother's school, but their call is cut off by an explosion. Ken ducks as the explosion rocks the phone booth. When he is unable to contact his father, he runs away. Oil tanks at a nearby refinery begin to explode, and from the smoke emerges Hedorah in its new Flying Stage. Yukio and Miki try to pursue Ken in their car, but find it has stalled just before they see sludge running down the windshield. The two bail from the car as it is pulled in by Hedorah along with surrounding traffic. Hedorah takes flight once more and passes over the school where Toshie teaches, causing the students to collapse and choke for air as the plants wither around them. Godzilla confronts Hedorah near a factory, grabbing it from the air and throwing it to the ground. Godzilla punches Hedorah, but the blow is harmlessly absorbed by Hedorah's amorphous body. Hedorah takes flight again, spraying its sulfuric acid mist directly into Godzilla's face, causing him to fall to the ground gasping for air as the factory explodes around him. Hedorah flies above a fleeing crowd, its sulfuric mist reducing them to skeletons in a matter of moments. The creature then flies over a construction site, melting the metal girders with its sulfuric acid mist.

In the aftermath of Hedorah's daytime raid, Fuji City is enveloped in toxic smog as casualties number in the thousands. Rescue workers are hindered by the smog, as bodies reportedly pile up in the streets. No time of day or place is safe from Hedorah, which against expectations came ashore on a clear day and now has the ability to fly. Humanity is left to wonder which new terrifying form the creature will assume. Yukio meanwhile has organized a party for the youth at the top of Mount Fuji in a final act of defiance against Hedorah before it conquers all of Japan. Back at his home, Toru struggles to think of any way of stopping Hedorah. Oxygen may deter its growth, but this seems insufficient to defeat it. Ken proposes that if Hedorah is made of sludge, they should be able to just dry it out. This suggestion gives Yano an idea. He places a small Hedorah between two electrode panels, a method utilized to dry fields in Hokkaido. He activates the electrodes, which release an electrical current that dries out the Hedorah in a matter of moments. With this method proving effective, Yano decides to contact the JSDF to reproduce the electrodes on a larger scale.

Ken attends the party at Mt. Fuji with Yukio and Miki but has a vision of Godzilla while he is there. He warns the others that Hedorah must be coming as well, which is proven to be true as the roars of both monsters are heard. Godzilla fires his atomic breath at Hedorah as it flies overhead, but it dodges the blast. Hedorah knocks Godzilla down with its Hedrium Light Ray then touches down and metamorphoses into its colossal Perfect Stage, which far exceeds Godzilla's size. Hedorah makes its way toward the partygoers. Yukio and the others throw torches at Hedorah, who retaliates by firing sludge at them, killing many of them including Yukio. Miki and Ken watch helplessly as Hedorah continues its advance. Godzilla confronts his now-larger enemy before it can reach the survivors, hitting a rock with his tail to distract Hedorah. When the monster turns, Godzilla plunges his fist into Hedorah's eye, which bleeds profusely before Hedorah forces it closed. Hedorah's acidic blood burns the flesh off of Godzilla's hand down to the bone. Hedorah counterattacks Godzilla with blasts of acidic sludge from its body which cost Godzilla his eye, and its deadly Hedrium Light Ray. Hedorah transforms into its Flying Stage and lifts and drops Godzilla into a pit, then changes back and proceeds to nearly drown Godzilla in sludge. Godzilla escapes the pit and the two monsters roll down the hillside, damaging the power lines powering the Giant Electrode nearby. Hedorah is drawn by flashing headlights in front of the Electrode and flies there. Yano and Toshie arrive after learning that Ken is in danger and watch as the JSDF works to get the Giant Electrode working in time. Helicopters try to distract Hedorah with oxygen bombs, but it blasts them out of the sky with its Hedrium Light Ray. Hedorah continues advancing toward the trucks flashing their headlights and passes in front of the Giant Electrode. Suddenly, Godzilla fires his atomic breath at the Electrode which powers it on. The electrical current causes Hedorah to writhe in agony before falling to the ground as a dried husk. Godzilla approaches the fallen Hedorah and tears out its eyeballs before powering on the Electrode once more. The eyeballs are reduced to piles of ash in Godzilla's hands. Godzilla inspects Hedorah's carcass before walking away. However, he strikes a rock into Hedorah's carcass with his tail, only for the husk to split open and a Flying Stage Hedorah to fly out. Godzilla calmly holds his arms apart and fires his atomic breath at the ground, causing him to lift off into the air. Godzilla chases down Hedorah and knocks it out of the sky. Hedorah transforms into its Landing Stage, but is no match for Godzilla anymore and is easily subdued. Godzilla grabs Hedorah and flies back to the Giant Electrode. The JSDF activates it but blows a fuse. Godzilla shakes his head in disappointment and again fires his atomic breath, powering on the Electrode. Hedorah is again dried into a husk, but this time Godzilla tears into it to expose every square inch of moisture that could reanimate into another Hedorah. He then activates the Electrode and completely dries out all of Hedorah's remains, leaving no chance of the monster coming back to life. Godzilla briefly turns his head toward the onlooking humans before walking away. Ken and Miki follow Godzilla as he walks down the slopes of Mt. Fuji, with Ken calling after his hero. While Godzilla is victorious, continuing rampant pollution means that the emergence of a second Hedorah may not be out of the question.