For thousands of years, with the advancement of science and technology, humans have been changing the world in order to create a better living environment for themselves. The increase in life span and the convenience of life have made humans more active in changing the world. Rapid changes also mean crises. Several crises have not stopped human thoughts. People are always thinking about me. I can do better, I can change the world. Finally, after a big crisis, mankind faced a desperate situation. Fortunately, the discovery of a new energy source allowed surviving humans to survive. However, humans had no choice but to start going underground, but people never gave up and returned to the surface. The pioneers who returned to the surface were also called "human walkers".
