Energy is the foundation for everything, but nobody imagined that one day, a man by the name of Shoji has discovered that the energy within someone can be used to manipulate the pure form of it or even a natural element like water and fire.
This power is greater than anything humans have ever discovered.
But with great power comes great responsibility, the UN tried to regulate it so that people with bad intentions couldn't wipe out everything in a split second.
However this failed. A war broke out which destroyed almost 90% of its land area and killed well over half of the entire human population.
Centuries has past and only parts of Africa and Eurasia are habitable.
The human race managed to keep itself together and formed one nation with borderless regions. This is to keep everybody feel united. Urban places have been made with elemental bending in mind.