The defining law of this universe is that human emotion has a physical weight. Every fear, from the mundane (tomatoes, sea cucumbers) to the primal (darkness, death), creates a corresponding Devil.
The Power Scale: A Devil’s strength is directly proportional to how much its name is feared. The Coffee Devil might be a harmless nuisance, while the Gun Devil can level entire nations in minutes.
The Cycle of Rebirth: Devils are functionally immortal. When a Devil is "killed" in the human world, it is immediately reincarnated in Hell. When it dies in Hell, it returns to Earth. They are an eternal part of the global ecosystem.
History has not progressed like ours. The constant threat of supernatural extinction has led to a world that feels "stuck" in a gritty, industrial loop.
Tokyo’s Commercial Districts: High-density hubs like Shinjuku and Shibuya are the heart of the story. They are characterized by a cluttered aesthetic of neon signs, overhead power lines, and a "lived-in" grittiness.
The Reconstruction Loop: Scaffolding and construction barriers are permanent fixtures of the city. As soon as a district is destroyed by a Devil, the government initiates rapid-reconstruction protocols to maintain economic stability.
Public Safety: In response to the Devil threat, national governments have established "Public Safety" divisions. These are bureaucratic, corporate-style organizations where humans (and the supernatural entities they employ) hunt Devils as a state-sanctioned career.
Life is categorized by five distinct types of entities:
Humans: Baseline population; source of all Devil power. Fragile; use Contracts to survive.
Devils: Monsters birthed from names/concepts. Powered by fear; reincarnate in Hell.
Fiends: Devils inhabiting a human corpse. Distinct head features; reduced power.
Hybrids: Humans fused with Devils via a trigger. Functionally immortal; weaponized forms.
Primal Fears: Ancient entities that have never died. Transcendent power; universal terrors.
In this world, safety is an illusion. Every major city is equipped with sirens similar to air-raid alarms. When a high-level threat is detected, the civilian population must evacuate to underground shelters immediately. This constant state of "Low-Level Terror" is what keeps the Devils fed and the cycle of violence turning.