In the year 1999, humanity begins to advance beyond the solar system. The planet Gishin, led by the Emperor Zule, which aims to conquer the galaxy, runs into conflict with Earth. He targets Earth for elimination and to do this, he sends a baby called Mars to live among humanity. Accompanying the baby is a giant robot named Gaia, which utilizes a new power source strong enough to destroy an entire planet. As planned, Mars is expected to grow up, where he will activate the bomb within Gaia to fulfill the mission of destroying the Earth. However, when Mars arrives on Earth his is adopted into a Japanese family and given the name Takeru. Seventeen years later, Takeru would grow up with a love for humanity and refuses to detonate the bomb as ordered by Zule. However, if Takeru was to die, the bomb within Gaia would explode destroying the earth.