As most of the major nations that existed two decades ago fell and the Alliance had to reorganize everything, a lot had to change.
As such, the former nations that managed to weather the disasters were renamed, adopting a simplified naming system to facilitate global administration. For example, the archipelago east of the Asian continent known as Japan is now referred to as J City.
This new nomenclature not only refers to the main city, but also encompasses the safe areas and adjacent territories controlled by the Alliance, for this reason the Safe Area where Kaito was born is called Z4, because it is the fourth Safe Area in the territory of City Z.
Each city was given a unique alphabetical designation, and these designations were adopted worldwide. The choice of letters was made based on geographical, historical, and cultural criteria, seeking to represent the unique identity of each region.
