In the year 2047, powerful metal ores called Gaimetal were discovered 50,000 meters (160,000 feet) beneath the earth. The mining business boomed around the world, after discovering that the Gaimetal produces high amounts of pure energy. However later in the year 2055, the metal ores were discovered to contain a dangerous potential. The Gaimetals can mutate into Gaists, metallic lifeforms whose bodies are entirely encrusted with Gaimetal. They emerged from the surface and began attacking people.
In 2064, the world's government founded the Gaist Crusher Garrison, a vanguard organization to counter against the Gaist threat. Coming forth to the present, a hot-headed middle schooler named Rekka Shirogane stands up to the challenge to suit up in Gaist Gear and battle over 100 varieties of Gaists around the globe.