── CHAPTER 1. Prelude to Disaster: The Korean Outbreak (PROLOGUE)

In August 2026, South Korean civilization was permanently paralyzed in just 72 hours. The root of all evil was the greed of a giant American private corporation seeking a monopoly on capital and its Korean branch, where their advanced bio-hub was located. Conducting illegal biological experiments funded by secret money smuggled from various countries, they plotted to leak a virus while disguised as victims to skyrocket the value of their own vaccine.

However, the virus mocked human calculations, undergoing explosive genetic rearrangement and mutation. The Seoul metropolitan area, boasting one of the highest population densities in the world, was the perfect incubator for the virus. Indiscriminate all-directional spread occurred through subway commutes and dense public transport infrastructure, and the government's emergency martial law and urban quarantine lines collapsed like dominoes. The Korean Peninsula, where administrative functions have vanished, is now an isolated hell filled with moving corpses.

── CHAPTER 2. Basic Physiology of the Infected (THE DEAD)

To survive in the Korean terrain where firearms are regulated, one must perfectly understand the biological limits and weaknesses of the infected.

Brain Destruction as the Sole Neutralization: The infected are in a state where all organ functions from their previous life have stopped. Since only the mutant virus that has seized the brain cells forcibly drives the body, they will not stop attacking even if limbs are severed unless the brain tissue is completely destroyed physically.

Biological Limits of Cell Necrosis: While it seems they can remain active for long periods without separate nutritional intake as the virus constantly supplies energy, host cell decay accelerates if there is no organic matter influx at all. Because of this, they have a weakness where their mobility dramatically decreases in extreme winter climates or perfectly isolated, sealed areas.

Sound Tropism and Micro-vibration Detection: Their vision and heat-sensing abilities are paralyzed, but their ability to capture subtle sounds and physical vibrations has evolved to a terrifying degree. Since they react immediately to even small frictional noises in alleys or inside apartments, survivors must attach thick cloth to the soles of their shoes to minimize vibration propagation during night activities.

Variability of Movement Speed: Depending on the host's physical state before death and the virus's activity level, their speed appears randomly from a normal walking pace to a near-sprint jogging speed, so a moment's lapse in vigilance leads to instant death.

── CHAPTER 3. Infection Mechanism and Close-quarters Environment (ENVIRONMENT)

Korea's environment, where private firearm ownership is impossible, forces survivors into extreme struggles.

Strong Fluid Permeability: There is no airborne infection, but the moment the contaminated blood or saliva of an infected person touches a wound or mucous membrane, transmission is immediate. Even trace amounts of body fluids seeping through gaps in clothing or old protective gear during combat must be absolutely blocked.

Fatality of Residual Material on Teeth: Concentrated viral material that does not die even at room temperature remains on the surface of the infected's teeth. Even a light abrasion or skin scratch will immediately collapse the body's immune system.

Forced Close Combat and Fortification: Survivors without guns must rely on cold weapons such as baseball bats, archery bows, and private blades. Accordingly, they have established a survival method of fortifying high-rise apartment complexes with sturdy concrete outer walls, welding fire doors shut, and moving silently using only balcony ropes to control noise to the extreme.

CHAPTER 4. The 0.01% Disaster: Special Variants (VARIANTS)

These are high-risk evolved entities that manifested with only a 0.01% probability, combining Korea's high-density environment with specific genetic traits. They release unique pheromones that accelerate the mutation of surrounding infected, so failure to kill them early leads directly to total annihilation.

1. Brute (Strength-Enhanced Type) Characteristics: A massive entity with abnormally fused and hypertrophied muscle tissue.

Risk: Its skeletal density is comparable to concrete, so normal cold weapon strikes do not work. With superhuman strength that transcends human limits, it breaks through steel fire doors of apartments or vehicle barricades with its bare body to clear a path for the horde.

2. Scout (Hearing-Sensitive Type) Characteristics: An entity with abnormally amplified auditory organs and cranial structure.

Risk: It captures even the faintest sound of breathing within a complex or the vibrations of stairs. Upon discovering a target, it emits a high-frequency scream to forcibly gather nearby zombies; this scream also causes extreme noise interference in survivors' analog radio systems, paralyzing communication networks.

3. Leader (Army-Commanding Type) Characteristics: A leader entity possessing a low level of tactical computational intelligence.

Risk: It perfectly utilizes the terrain of complex large-scale apartment complexes or maze-like Korean alleys. It employs organic military-style tactics, such as ordering subordinate infected to ambush or pre-emptively blocking survivors' escape routes.

4. Runner (Speed-Enhanced Type) Characteristics: An entity with a lightened skeletal structure and explosively evolved lower body muscle fibers.

Risk: It sprints at speeds approaching a driving vehicle and scales walls freely. In particular, it is capable of vertical breakthroughs to upper floors by climbing gas pipes on apartment exterior walls, ambushing survivors in high-rise safe zones from the rear.

5. Guardian (Hard-Armored Type) Characteristics: An entity whose skin tissue has hardened into a biological armor as tough as bone.

Risk: It deflects firearm shots or cold weapon strikes head-on. Since the shock-absorbing cell layer beneath the armor perfectly protects the head, a frontal weak point attack is impossible unless the bio-armor is first stripped away using traps or heavy weaponry.

── CHAPTER 5. The Few Humans of the Peninsula: 5 Types of Immunity Classification (IMMUNITY)

With the majority of the population turned into corpses, there exists a very small minority of humans who resist the virus through a miracle of genetic sequencing. Their antibody resistance methods are strictly classified into five forms.

TYPE 1. Incomplete Single-use Immune: Upon the first exposure to infection, they forcibly suppress the virus and avoid instant death. However, there is a high probability of death from shock due to high fevers exceeding 40 degrees and pain for 48 hours, and even after recovery, serious permanent aftereffects such as chronic motor impairment or tinnitus remain. It is a one-time antibody that results in certain infection if bitten again.

TYPE 2. Complete Single-use Immune: Upon the first infection, they perfectly eliminate the virus without any symptoms or aftereffects. However, since it is only a one-time shield, if they overconfidently expose themselves to a second source of infection, their immune system collapses immediately, and they turn into an infected entity 100% rapidly.

TYPE 3. Incomplete Multiple Immune: They do not turn into zombies even if bitten multiple times or if body fluids enter their system. However, every time the virus invades, the antibodies in their body clash violently, causing fatal chills, coughing up blood, and shock-level pain each time. Their organs age rapidly with every instance, and they typically die from immune system limits after five or more cumulative contacts.

TYPE 4. Complete Multiple Immune: An exceptionally rare constitution that is hard to find; they maintain a perfect asymptomatic defense state without pain or transformation even after multiple exposures. However, these antibodies cause extreme rejection when fused with another person's blood, making them unusable as raw material for a universal vaccine. It is a personal-specific immunity lived with the loneliness of being unable to save others.

TYPE 5. Absolute Immune (Ultra-rare in Korea): The master key to rebuilding civilization, with only 10,000 existing worldwide. Besides permanent immunity, the unique hormones secreted from their cells cause the infected to mistake them for 'fellow zombies.' They are a core asset capable of tactical operations like luring or bypassing zombies, as they are not attacked first even when walking through the middle of a horde.