[1] The story takes place at the dawn of the 21st century, when a terrorist organization known as Gigantic Rebellion Operators (GRO) utilizes giant robots built by an ancient civilization known as "GRs" to cause fear and destruction around the world.

Meanwhile, the United Nations paramilitary organization UNISOM attempts to discover and secure hidden ruins containing GRs before GRO can obtain them.

The independent 24/7 news organization known as Broadcasting Frontline Network (BFN) reports on the conflict between GRO and UNISOM, always seeming to have more information than they should.

Beckoned by forces that he cannot understand, Daisaku is made to bond, body and spirit, with the ancient weapon and fight against GRO, discovering the truth behind the conflict and the nature and purpose of the GRs along the way.

[2] Due to a change in staff at SoftGarage, the idea of a faithful adaptation of Giant Robo was scrapped in favor of a modern worldview.