A strange incidence of genetic alteration was then discovered after the upheaval. A large amount of the population born after the incident inherited special powers due to the radiation given off from underneath the Earth’s crust. The explanation for these "powers" is still unclear but a new breed of humans and humanoid like species have emerged from the natural disaster.

After the catastrophic incident, the city of Sukurideo was abandoned and treated as a foreign state by the main Japanese government. Most of the topology of the land is in ruins, and everything within the city is either very old or broken. Because of this, people have reverted back to the old Japanese ways of living. Sure, guns, cars, electricity, and other modern day things are still around, but they arnt as common as they once where and there isnt as much.

Before long, Demon and Half-Demon started to roam about. It is still unclear where they came from but some people believe they heard Sukuriedo was abandoned. Since they where already banned from where they used to live by humans, it is said they thought the Lost City would be a good place to live without the constant worries of the humans turning on them. They still try to lay low for they do not wish to strike fear into the hearts of the remaining humans still living in the lost city.

A number of these "new breeds" of humans and humanoid like beings exist within the slums of the Lost City. Many of them run amuck, abusing their abilities and powers. To mitigate the effects of these renegade beings within the area, the police organization known as SDT was formed by the Japanese Goverment to restore order. As their primary objective, SDT is to suppress, punish and sometimes capture any threats to society. Those that are incarcerated have two choices. Either join STD and hunt your own kind or be confined indefinitely.