His father Professor Shiba, a talented scientist and archaeologist, manages to restore him to life by means of a powerful relic from the ancient and mysterious Jamatai Kingdom, a bronze bell which is hidden inside Hiroshi's body and turns him unknowingly into a sort of cyborg.

Her henchmen kill Prof. Shiba in vain pursue of the artifact, barely leaving the scientist time to upload his thought on a supercomputer at a specially built defense base.

In such battles, Jeeg is also aided by a robot horse known as Panzeroid, and a fighting jet capable of shooting replacement components and specialized weapons for his body.

Steel Jeeg is formed by combining the parts released by the Big Shooter jet, piloted by Prof. Shiba's young assistant, Miwa Uzuki.

A complete and original intro theme called "El Vengador" (The Avenger) was composed and sung by musician Memo Aguirre for the Spanish dub of the series released in Latin America.