Neighbor

A Neighbor is an interdimensional and extraterrestrial race of humans and humanoids that live within the Neighborhood, living within separate planets opposite to Earth. While most neighboring planets have inhabitants that appear like regular human beings, others have inhabitants that are humanoid in appearance, but have different (and in the country of Spinthir's case, radically different) physical traits that distinguishes them and make them overall less human, if not completely inhuman. This along with the fact that they are from separate worlds makes them a completely unique species altogether. They were accused of attacking Mikado City four years prior to the start of the series, thus causing stigma towards them.

Calvaria vs. Spinthir
Some time before, Spinthir had invaded another nation, Calvaria. Yūgo and his son Yūma fought on the side of Calvaria, on behalf of Yūgo's friend Raymond. Three years after Yūgo's death, the war ended with Calvaria's victory.

First Large-Scale Invasion
An unknown nation sent Trion Warriors to Mikado City, resulting in the city's near-annihilation if it weren't for Border, a mysterious organization that used Triggers, Neighbor technology to defeat them. Many people were killed or went missing. Border was set up as a protection agency.

Large-Scale Invasion Arc
The old god of Aftokrator, who powered the Queen Trigger of Aftokrator, was dying, and Aftokrator was in a crisis of looking for one. It was decided that the four major families would lead expeditions to find a god, but in case one could not be found, Hyrein planned to suggest House Ellin's head as god.

Known Neighbors
Format: name (allegiance)
 * Yūma Kuga (Border)
 * Replica (Border)
 * Raymond (Calvaria)
 * Izukacha (Calvaria)
 * Vittarno (Calvaria)
 * Hyrein (Aftokrator)
 * Mira (Aftokrator)
 * Hyuse (Border, formerly Aftokrator)
 * Viza (Aftokrator)
 * Lamvanein (Aftokrator)
 * Enedra (Border, formerly Aftokrator)
 * Gatlin (Galopoula)
 * Koskero (Galopoula)
 * Wen Sō (Galopoula)
 * Reghindetz (Galopoula)
 * Ratarikov (Galopoula)
 * Yomi (Galopoula)
 * Yōtarō Rindō (Border, formerly Aristera)
 * Ruka Shinoda (Border, formerly Aristera)
 * Xeno (None) (Anime only)
 * Lilith (None) (Anime only)
 * Gieve (Ergates) (Anime only)
 * Charon (Ergates) (Anime only)
 * Lamia (Ergates) (Anime only)