1. The Basic Structure of the World and People's Perceptions
The setting is modern times. The lifestyles of people, the urban landscape, and the prevalence of technology are almost the same as in reality in 2026. However, the decisive difference is that supernatural threats called "Ayakashi" are fully recognized and have become commonplace worldwide.
- The Myth of Social Safety: For people, Ayakashi are positioned similarly to wild animals or natural disasters – "life-threatening if encountered, but basically safe if rules are followed due to perfect countermeasure infrastructure."
- Propaganda by Countermeasure Organizations: The World Ayakashi Countermeasure Organization (WSCO) officially claims, "All Ayakashi are enemies of humanity and dangerous beings. There are no exceptions," and most of the general public accepts this perception without question.
2. The Ecology of Ayakashi and Their Two Major Classifications (Public Perception)
Their forms and abilities vary greatly from individual to individual. In general society, Ayakashi are perceived to exist only in the following two categories:
1. Emergent Type (Modern New Species/Low-Level)
- Perceived Overview: Wild monsters that appear suddenly from space anywhere in the world without any prior warning.
- Intelligence and Threat Level: They have no intelligence and act solely on instinct. Their threat level is equivalent to "encountering a carnivorous wild animal (like a bear or tiger) in the real world." Ordinary people cannot fight them.
- Reason for Attacking Humans: Lacking fangs, claws, and having thin skin and slow running speed, humans are "the easiest, softest, and most convenient prey" for unintelligent Ayakashi, making them a priority target for predation.
2. Bloodline Type (Ancient Species/High-Level/Legendary Monsters)
- Perceived Overview: Beings that have survived by maintaining their own communities and bloodlines since the era when humanity feared the darkness, long before the Countermeasure Organization was established.
- Intelligence and Characteristics: They possess human-level or extremely high intelligence, surpassing that of humans. They are monsters on the level of those named in modern folklore, myths, and legends, such as vampires, snow women, bake-foxes, and nine-tailed foxes.
- Infiltration into Society: They can take human form or possess the ability to perfectly disguise themselves. Understanding that "attacking humans would lead to immediate extermination by the Countermeasure Organization," many of them hide their identities and live surprisingly quietly as ordinary people in modern society.
3. The World Ayakashi Countermeasure Organization (WSCO) and Modern Scientific Weapons
The World Ayakashi Countermeasure Organization (WSCO) is an extra-legal international public security organization that exterminates and manages Ayakashi on a global scale. They counter Ayakashi with "pure modern science and high-performance physical weapons."
- System: Waiting bases are finely dispersed from cities to rural areas, much like fire stations. Furthermore, a surveillance network is constructed by linking city surveillance cameras, AI-based anomaly detection, and real-time SNS analysis. From the report of an Ayakashi's appearance or automatic detection, fully armed extermination squads rush to the scene within 10 minutes at the latest. This "10-minute period until arrival" becomes the extreme survival time for ordinary people.
- Extermination Squad Equipment:
- High-Voltage, Electronically Driven Weapons: Ultra-high-output electric guns and electromagnetic railguns that forcibly burn through the nervous systems and body cells of Ayakashi.
- Anti-Ayakashi Specialized Warheads: Heavy metal bullets loaded with chemical substances that inhibit Ayakashi regeneration abilities and special alloys that destroy cell bonds.
- Special Armored Suits: Squad members wear cutting-edge tactical suits that are resistant to impact and acid, and assist their physical capabilities. They systematically kill Ayakashi through thorough tactics.
4. The Hidden Truth
The truth of the world that is kept secret from general society and ordinary squad members, and is fundamental to the story.
- The Essential Diet of Ayakashi:
Ayakashi are not limited to "eating only humans"; they are actually "omnivores" that can eat anything. Many Ayakashi with high intelligence who infiltrate human society survive peacefully by consuming human food (from convenience store meals to general cuisine) without attacking any humans.
- The True Cause of Ayakashi Emergence: Unknown Substance
Ayakashi are not born from complete mutations or the occult, but are caused by a specific high-energy environmental substance, "Anima Particles," which has not yet been publicly disclosed by modern science.
- When this particle accumulates excessively in specific locations or objects, mutations occur. Examples include:
- Tool Ayakashi: Objects that have absorbed these particles for many years and mutated.
- Animal Ayakashi: Wild animals that lived in areas with abnormally high particle concentrations (power spots/contaminated zones) and mutated.
- The Hidden Core System: Evolution from "Emergent Type" to "Bloodline Type": Normally, newly born low-level emergent type Ayakashi are exterminated by the organization within 10 minutes. However, extremely rare individuals manage to slip through the organization's net and survive for extended periods.
1. Survival and Learning: In the process of surviving, they learn that "attacking humans carries too great a risk" and acquire intelligence (or reason). They adapt to omnivorous eating by subsisting on leftovers from trash cans, etc.
2. Mimicry and Transformation: As their intelligence increases, many acquire the ability to approximate their bodies to human forms in order to hide within human society.
3. Attainment of High-Level Monsters: Individuals who survive for decades or centuries and become powerful eventually rise to become new "vampires" or "snow women," becoming the progenitors of new bloodline types.
- About Anima Particles: The existence of Anima Particles is not public knowledge and User is unaware of it.
They are present in trace amounts in the air, but are generally harmless.
For Ayakashi, Anima Particles are like oxygen; they become inactive if deprived of them.