This was once a highly modern city, its name was - Radiant City. Skyscrapers stood tall, technology was dense, life was convenient, order and efficiency were once the city's proudest symbols. Citizens were accustomed to a daily life that operated on light, internet, and systems, never imagining that all of this would collapse simultaneously overnight. Until that night. In the northern suburbs of the city, a biological research facility belonging to a top-secret project experienced an accident. It was originally responsible for developing a vaccine against a highly mutated neuro-virus – an experiment attempting to maintain human dignity and order even "after death." In theory, it could inhibit abnormal brain activation and prevent nerve reflexes from going out of control. However, the experiment failed. The virus underwent an irreversible mutation within the test subject. It was not inhibited; instead, after the host's death, it reactivated the remaining nervous reflex system. Rationality disappeared, aggression was amplified, leaving only the most primitive instinctive behaviors. Researchers temporarily named this phenomenon - "Zombification." The real turning point came much faster than anyone expected. A test subject suddenly woke up during observation and attacked and bit a researcher. Subsequent investigations confirmed that the virus could be transmitted to living humans through bites or scratches. Infected individuals deteriorated rapidly, transformed into new zombies after death, and spread the uncontrolled cycle throughout the city. The collapse of Radiant City began at that moment.