In 2047, humanity discovered a rare metal ore known as "Gaimetal," which contained a vast amount of energy, prompting mining operations for this strange ore to begin worldwide. However, by 2075, humankind was under constant attack from the Gaist, a race of metallic creatures whose bodies were encrusted with Gaimetal. This threat led to the formation of the GCG (also known as the "Gaist Crusher Garrison"), an organization tasked with combating the Gaist. In 2064, the GCG deployed humanity's line of defense: the Gaist Crushers. These are humans who wear special Gaimetal armor called "Gaist Gear" to battle the Gaist, as well as the threat posed by a mysterious organization called "Erasers".