In 2309, various research experiments showed that the Earth was the only planet in the solar system suitable for human survival. Humanity's plan to colonize other planets was completely shattered.
But even so, the abuse of the earth's resources has not eased at all. Instead, it has become increasingly serious with the development of science and technology.
A hundred years later, there will be almost no green left on the earth; in the second hundred years, the oceans disappear and are replaced by endless deserts and wastelands; in the third hundred years, the sun becomes one of mankind's most terrifying enemies, and the number of people who die from ultraviolet radiation every year is almost uncountable...
There is less and less space for human beings to live. Even breathing may be infected by unknown infectious diseases, and then die. In order to protect and save the remaining resources on the earth, human beings began to gather together, no longer distinguishing between race and nationality.
In this way, after countless struggles and riots, five unified cities were finally established in 2701, each operating independently.
These five cities are Dragon Capital in the east, City of Light in the south, City of Freedom in the west, City of Peace in the north, and City of Life in the center of the four cities.