30,000 Miles Under the Sea 1970

Isamu, a young boy whose father is a marine researcher and director of a marine research institute located on a volcanic island, lives with his parents, including Isamu’s Mother, who works as his father’s assistant. One day, he explores the ocean floor with his pet cheetah before heading toward the island’s volcano. There, he encounters a mysterious girl dressed in a bright red outfit.

An earthquake suddenly strikes, and a giant robot monster known as the Flame Dragon emerges from the volcanic crater. As the creature begins attacking the surrounding area, the girl summons a robot called the See-Through to rescue them. Two men emerge from the machine and introduce themselves as Octopus and Tuttle, the girl’s bodyguards. The girl reveals her identity as Angel, princess of the undersea kingdom of Atlas, a civilization located at the bottom of the ocean. Isamu and his pet are invited to visit Atlas aboard the See-Through.

Meanwhile, the ruler of the Undersea Kingdom becomes concerned after learning about the Flame Dragon. He explains that the Atlasians originally lived on land until King Magma I attempted to conquer the surface world by creating the Flame Dragon. However, the weapon went out of control and destroyed their country. As a result, Magma I’s followers retreated underground, while the remaining Atlasians established their kingdom beneath the sea. The “Flame Dragon” seen by Isamu is revealed to be a robot constructed by King Magma VII, a descendant of the underground faction.

Determined to stop the threat, Isamu and his companions pursue the Flame Dragon to the Underground Kingdom but are captured and imprisoned. They eventually escape and reach the control center, where King Magma VII operates the Flame Dragon. At the same time, the underground kingdom launches an assault on the undersea kingdom using an army of Flame Dragons. While the undersea military struggles to defend their realm, Isamu confronts Magma VII, defeats him and activates the control system, causing the Flame Dragon army to turn against the Underground Kingdom. The ensuing conflict results in the destruction of the underground kingdom and the Flame Dragons, restoring peace beneath the sea.

After the battle, Isamu and his pet return to the surface aboard the See-Through. Shortly afterward, volcanoes around the world begin to erupt violently. The surface world remains unaware that these events are connected to the massive underwater war and the destruction of the Underground Kingdom.