On November 8, 2018, an anomalous thunderstorm struck N City, located within a highly active geomagnetic layer. This event subtly altered the geomagnetic reactions, triggering a theoretical magnetic field black hole effect that transported the entire city back 75 million years to the Cretaceous period! The massive EMP (electromagnetic pulse) caused by the magnetic field effect destroyed a vast number of electronic products, instantly collapsing the technological systems upon which modern civilization relies. With the paralysis of infrastructure such as communications, electricity, medical services, and transportation, the city plunged into extreme panic and chaos. When familiar yet alien prehistoric creatures appeared before people's eyes and began slaughtering indiscriminately, humanity realized that in the Cretaceous period, humans were no longer at the top of the food chain. Accustomed to being predators, humans suddenly found themselves transformed into prey, and only then did they recognize their own insignificance. Even more despairingly, as the moral and legal systems humans depended on gradually crumbled, the true threats were no longer just the terrifying creatures and environment of this era, but also their fellow humans. Every person in this city holds their own creed for survival! Will they trust no one but themselves, or rely on trusted companions to survive? People of all kinds demonstrate the will to survive and the skills unique to intelligent beings. How will they manage to survive in this lost city? Or will they ever escape this lost metropolis?