| This article is based on information from Japanese-only media.|
The following content has not been released in the English language, so details are subject to change at any given time.
Although Regnum's territory is not clearly defined, its capital city that shares its name rests in the center of the world and, like many capitals, near the sea. Two notable locations include Regnum Cavern and the Western Battlefield. Located beneath the capital, Regnum Cavern is a water-filled series of tunnels that are said to house a rare mushroom. Hermana Larmo recruits the group into helping her locate the mushroom so that she may sell it and help feed herself and the homeless children for whom she cares. The cavern also houses a memory circle, which the group uses to gain more insight into their past lives. The Western Battlefield lies just west of the capital city, separating the country from its warring neighbor, Garam. It is here where Ruca, Illia Animi, and Spada are forced to fight for the Regnum army against Garam soldiers, having been previously tested at Naohs Base. The small island country of Galpos is governed by Regnum due to having lost in the war. Likewise, the holy city of Naohs is settled within Regnum territory and is considered to be an extension of the powerhouse country.
Regnum is a highly-industrial nation that serves as the leader of the world. Because of its high pride and powerful voice for other countries, its relationship with the countries of Garam and Tenos is poor, resulting in the world war the game's plot heavily revolves around. An authoritarian nation, Regnum is strict with its veiled caste system of nobles, the general public, and the many homeless children that roam the streets. On the other hand, Regnum is also one of the most industrial countries in the world, possessing a well-developed transportation system, the technology of which it adopted from Tenos. Throughout the story, Regnum is frequently seen being officiated by an unnamed privy council that enacts a detainment law for the Reborn due to Arca's influence. This law is enforced under the pretense that the Reborn are a danger to society and should be detained for the public's safety. The reality, however, is that these captured Reborn are being used as tools for war.
- Many locations in the game mirror real-world locations. Regnum shares many similarities with the United States, being industrial in nature, possessing colonies, and having a large military. The U.S. unlawfully annexed the state of Hawaii, which is mirrored through Regnum's colonization of Galpos.