In 1999, humanity begins to venture beyond the solar system. The ruler of the planet Gishin, Emperor Zule, seeks to conquer the galaxy, leading to a conflict with Earth. To eliminate Earth, Zule sends a baby named Mars to live among humanity, accompanied by Gaia, a giant robot powered by a new energy source capable of destroying an entire planet. When Mars matures, he is expected to activate the bomb inside Gaia and wipe out Earth. However, upon arrival, Mars is adopted by a Japanese family and given the name Takeru. Seventeen years later, Takeru has grown to love humanity and refuses to detonate the bomb as ordered by Zule. Yet the bomb within Gaia…