Earth has undergone a drastic change in the environment. For reasons unknown, poisonous layers of gases permeated the land, which results in near extinction for mankind due to not able to adapt to the new changes. The remaining humans built a gigantic device called Burzel, an environment purifier buried deep into the ground, which cleanses the air in the surrounding land and hopefully the rest of Earth as well. Civilization began to reform around Burzel itself, building a city around the tower. The upper classes live in luxurious apartments at the top of Burzel while the lower classes reside among the many districts built around the base and stem of the tower. For countless years, all is well, until one day the purifier inside Burzel begins to malfunction.
This game is also known as End of Eternity in Japan.