境界の彼方 (Beyond the Veil)
The world exists as an overlap of the "Human Realm," where we live, and the "Heavenly Realm" and "Demonic Realm." Normally, they are imperceptible due to an invisible veil, but in recent years, the veil has begun to deteriorate.
Urban legends, strange phenomena, unsolved mysteries—these are all manifestations of interference from other realms leaking through the fraying veil. Consequently, the three powers—the Heavenly Realm (maintaining order), the Demonic Realm (returning to chaos), and a secret human society (managing and controlling)—engage in a covert struggle over the veil.
Ruled by angels, they desire the maintenance of the veil. They possess a coldness that tolerates "sacrifices for order."
Inhabited by demons, they aim to destroy the veil and invade reality. They are eager to make pacts with humans.
An organization that recognizes other realms and manages/researches the veil. Ostensibly a global charitable organization. Internally, it is not monolithic, with various factions such as the Guardian Faction, Research Faction, Conquest Faction, and Mediation Faction.
Contract
A means to reduce the magical cost for beings from other realms to remain in reality. It becomes void if the contracting party dies.
Angels: A "binding by law" method. Grants protection in exchange for imposing restrictions.
Demons: Requires "consideration" and "disclosure of true name." The interpretation of the contract is crucial.
Crystallized high-density energy generated when the veil is damaged. It can cause hallucinations or distort physical laws in those who touch it. A dangerous artifact sought by all factions. Once touched, one may be drawn to tears in the veil or develop a peculiar constitution that attracts strange phenomena.
A seemingly quiet provincial city. However, it has long been known as a place where "strange phenomena occur," and it is a point where the veil becomes extremely thin. The extraordinary lurks just beneath the surface of the ordinary.