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

In August 2026, South Korean civilization was permanently paralyzed in just 72 hours. It all started with the greed of a giant American private corporation seeking a capital monopoly and their Korean branch, where a high-tech 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 mutations. The Seoul metropolitan area, boasting one of the highest population densities in the world, was the perfect incubator. Indiscriminate 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 Only Neutralization: The infected are in a state where all organ functions from their previous life have stopped. Since the mutant virus that seized the brain cells forcibly drives the body, they will not stop attacking even if their 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 nutrition because the virus constantly supplies energy, host cell decay accelerates if there is no organic intake 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 minute 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 condition before death and the virus's activity level, they appear randomly with speeds ranging from a normal walking pace to a near-sprint jogging speed, so carelessness leads to instant death.

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

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

Strong Fluid Permeability: There is no airborne infection, but the moment the infected's contaminated blood or saliva touches a wound or mucous membrane, infection is immediate. Even trace amounts of fluid seeping through gaps in clothing or worn-out protective gear during combat must be absolutely blocked.

Fatality of Residual Matter 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 exterior walls, welding fire doors shut, and moving only via balcony exterior ropes to control noise to the extreme.

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

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

1. Brute (Strength-Enhanced Type) Features: A giant individual with abnormally fused and enlarged muscle tissue. Danger: With bone density comparable to concrete, general cold weapon strikes do not work. Using strength that transcends human limits, it breaks through steel fire doors of apartments or vehicle barricades with its bare body to open paths for the horde.

2. Scout (Hearing-Sensitive Type) Features: An individual with abnormally amplified auditory organs and skull structure. Danger: Captures even the sound of faint breathing within the complex or vibrations on stairs. Upon discovering a target, it lets out 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) Features: A leader individual possessing a low level of tactical computational intelligence. Danger: Perfectly utilizes complex large-scale apartment complexes or maze-like Korean alleyway terrain. It employs organic military-style tactics, such as directing subordinate infected to ambush or pre-emptively blocking survivors' escape routes.

4. Runner (Speed-Enhanced Type) Features: An individual with a lightweight skeleton and explosively evolved lower body muscle fibers. Danger: 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) Features: An individual whose skin outer tissue has hardened into biological armor as tough as bone. Danger: Deflects firearm shots or cold weapon strikes from the front. Since the shock-absorbing cell layer beneath the armor perfectly protects the head, a frontal weak point attack is impossible unless the biological armor is first stripped away using traps or heavy weapons.

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

Now that the majority of the population has turned into corpses, a very small number of humans exist who resist the virus through a miracle of genetic sequencing. Their antibody resistance methods are strictly classified into five forms.

TYPE 1. Incomplete Single 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 fever 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 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, turning them into an infected individual 100% rapidly.

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

TYPE 4. Complete Multiple Immune: An extremely rare constitution that is hard to find; they maintain a perfect asymptomatic defense state without pain or transformation even after multiple exposures. However, this antibody causes extreme rejection when fused with another person's blood, making it impossible to use as a 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. In addition to 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 such as luring or bypassing the infected, as they are not attacked first even when walking through the middle of a zombie horde.