30,000 Miles Under the Sea

King Magma VII is a descendant of King Magma I, who originally attempted to conquer the surface world using the Flame Dragon weapon. Although Magma I's plan failed and destroyed their original land, his followers retreated underground and established the Underground Kingdom. Magma VII seeks to finish what his ancestor started by using an army of Flame Dragon robots to attack both the surface world and the undersea kingdom of Atlas.

The Flame Dragon is not a living creature but a giant robot constructed by King Magma VII. It is controlled from a central control center within the Underground Kingdom. The robot can be operated remotely and was designed as a weapon capable of massive destruction. Magma VII uses an army of these Flame Dragons to launch attacks against both the surface and the undersea kingdom.

Earlier in the story, the ruler explains that King Magma I originally created the Flame Dragon as a weapon to conquer the surface.

The Atlasians are descendants of survivors from King Magma I's failed conquest attempt. When the Flame Dragon weapon went out of control, it destroyed their original kingdom on land. The survivors retreated underground and eventually established the undersea kingdom of Atlas beneath the ocean. They chose to live underwater to escape the devastation caused by the Flame Dragon and to remain hidden from the surface world.

Isamu confronts Magma VII directly at the Flame Dragon control center. After defeating him in combat, Isamu activates the Flame Dragon control system itself. By taking control of the system, Isamu is able to command the Flame Dragon army to turn against their masters in the Underground Kingdom, causing the robots to attack their own creators.

The timeline shows Isamu and his companions escaping imprisonment to reach the control center where Magma VII operates the Flame Dragon.

The movie implies that the massive underwater war and the destruction of the Underground Kingdom have global repercussions. When Isamu activates the Flame Dragon control system and the dragons turn against the underground kingdom, the resulting destruction creates seismic disturbances that trigger volcanic eruptions worldwide. The surface world remains unaware that these events are connected to the underwater conflict.

The earlier earthquake that summoned the first Flame Dragon from the volcanic crater hints at the connection between underground activity and the surface world.

The See-Through is a submarine vehicle used by the Atlasians for travel between the surface and their undersea kingdom. It is large enough to carry passengers, as Isamu and his pet cheetah are invited aboard to visit Atlas. The vehicle has a transparent section, which likely gives it its name, allowing passengers to see the ocean surroundings during the journey.

Isamu reaches the Flame Dragon control center where Magma VII operates the machines. After defeating Magma VII, Isamu activates the central control system that commands all Flame Dragons. By hacking into this system, he reprograms the robots to attack their own masters. This strategic act turns the tide of war, destroying the Underground Kingdom and ending the threat to Atlas.

The timeline establishes that the Flame Dragons are controlled remotely from a central system, which becomes the key to Isamu's victory.

Isamu was present when the Flame Dragon first appeared near his home on the volcanic island. As the son of a marine researcher who directs a research institute on that island, he has a natural connection to the ocean. Angel, the princess of Atlas, encountered him during the initial attack and recruited him for his courage and willingness to help. His unique position as someone from the surface world made him essential to the mission against the underground threat.

The opening scenes show Isamu exploring the ocean floor with his pet cheetah, demonstrating his adventurous nature and connection to the sea.

King Magma VII is a direct descendant of King Magma I, the original ruler who attempted to conquer the surface world. When Magma I created the Flame Dragon weapon, it went out of control and destroyed their kingdom. His followers retreated underground and established the Underground Kingdom. Magma VII, as a descendant of this lineage, carries on his ancestor's ambition to conquer the surface world using improved versions of the Flame Dragon robots.

The ruler of the Undersea Kingdom explains this historical connection when recounting Atlas history to Isamu.

The Underground Kingdom is completely destroyed as a result of the battle. When Isamu activates the Flame Dragon control system, the robots turn on their creators and attack the underground kingdom. This destruction ends the threat from the underground faction and restores peace beneath the sea. However, the ending suggests this victory comes with consequences, as evidenced by the global volcanic eruptions that follow.