Although Black Snake Is a First-Class Killer, Killers Also Need to Rest.

In the last days of 2218, the environment is seriously polluted. There are less than a billion people on Earth. People all over the world gathered in places where they could see green and established a unified world government. In addition to the world government, there are also some local organizations and mercenaries who separate forests and water sources. Two top killers, Black Snake and Xiao, were ordered to find DR. Lee who could change the water source...