The War of the Gargantuas

A sailor rescued at sea falls into a suburban hospital in a state of shock. Barely collecting his thoughts, he tells doctors and investigators about how his yacht was caught in the sea by a typhoon the day before, and soon attacked by a giant octopus. The monster could have sunk the ship if Frankenstein had not appeared, destroying the octopus after a short battle. After that, Frankenstein sank the yacht, fished out and ate all the people, and only he managed to escape. Investigators don't believe the sailor's story: they believe that Frankenstein has disappeared and will never appear again.

The next day, in a wide bay, in front of the crowd, a huge green giant appeared out of the water and drowned the ship. This attracts the attention of the police, but for a while the investigation does not bring any results. Later in the evening, the same giant appears from the sea already near the airport located in the coastal zone, where, sowing unimaginable panic, it begins to catch and devour people. However, soon he unexpectedly, as if afraid of something, runs back to the sea.

News of a strange monster, very reminiscent of Frankenstein, soon reaches geneticists Yuzo Madzida and Akemi Tagawa, who previously studied Frankenstein. An investigator comes to them and asks a number of questions about the possibility that Frankenstein survived the fight with Oodako. Akemi and Yuzo categorically deny that the new monster that has appeared is Frankenstein, since the object of their research did not hunt people.

Some time later, the green monster reappears, and a sample of his tissue is delivered by Yuzo and Akemi. They investigate it and come to the conclusion that it is a new creature that has emerged from Frankenstein's cells, to which the name Gaira is assigned.

Later it turns out that Gayra is afraid of sunlight and cannot stay out of the water for a long time, which the military decides to use against him. Gair manages to lure him to land, to the forest, where an attack is launched on him. Rockets and maser beams cannot stop the Gyre, only electric impulses launched through river water harm it. Gayra begins to weaken, but then suddenly a monster with brown fur similar to him appears. He pulls Gayra out of the water and together they hide in the forest.

When Akemi and Yuzo find out about what happened, they come to the conclusion that the new monster is also a descendant of Frankenstein, but he does not live in the water, but in the mountains. He is given the name Sanda.

In search of monsters, Yuzo and Akemi go to the Japanese Alps, where they soon find Sandu and Gaira. Gayra behaves very aggressively and almost attacks Sandu, but he drives him into a mountain lake. Akemi almost falls into the abyss, but Sanda, who came to her rescue, helps her get out. Sanda, it turns out, inherited from Frankenstein not only his appearance, but also his peaceful nature.

Upon returning to the city, Akemi and Yuzo convince the military not to attack Sandu, but to attack Gaira; they agree.

Gaira appears in Tokyo, despite the fact that the light scaring him is turned on everywhere. Gayra, in a rage, begins to destroy everything. Soon Sanda appears and at first tries to take her brother out of the city without any clashes. But the battle is inevitable – a fight ensues.

The battle is going on with varying success, Akemi and Yuzo, who happened to be nearby, miraculously remain alive, and with the onset of morning, both monsters hide in the ocean. Soon Akemi and Yuzo get the news that Sanda and Gaira were seen fighting in the open ocean, but both died after falling into the zone of an underwater volcano.