[3] In the near future, after the world population and economy is devastated by a series of simultaneous hypercanes,[a] many different factions and fledgling nations appear.

These special zones were created with the help of Power Assist Technology,[c] which allowed Japan to recover from the consequences of the worldwide disaster (which included a combination of land subsidence and rising sea levels resulting in the permanent submerging of low-lying areas and a subsequent ice age in much of the Northern Hemisphere), albeit to a strictly limited degree.

The Revenus are generally restricted[g] from entering the special zones, causing tension which creates a resistance movement which fights back against the Logos.

With the tagline "A Near Future Late-Shogunate Action Animation", the story draws analogies with 19th-century Japan at the end of the Tokugawa Shogunate period, just before the Boshin War.

Jō and Jin defect from Phantom, an elite Japanese military special operations group which is used to help control the Revenus.