In 2050, Earth faces a severe energy crisis. A brilliant scientist in Trinity City discovers the Trinity energy, a new power source capable of meeting the world’s entire demand. The alien empire of the Elda learns of this breakthrough and plans to seize it by force. They attack Earth's space colony on Jupiter’s moon Io, seize control, and threaten global stability. At the same time, the Trinity energy is harnessed to build three giant robots that merge into the formidable God Sigma, piloted by martial artist‑turned‑pilot Dantou Shiya. With its mighty sword, God Sigma now stands as the last line of defense between Earth’s peace and the Elda’s aggressive ambitions.