Soon after World War 2, the gates in which monsters stayed opened to the people of Earth.This monsters only seek carnage and are even hostile to each other.
Humans awakened a system which aloud them to be players, only 43.5% of the world at least. Just like how the United Nations governs all the countries, the United Player Union governs every player.
Nothing changed much from the original Earth. U.S.A, Russia and China are still the strongest countries. Then there is Australia which is currently the richest country in the world, I said richest, not powerful.
The gates didn't only bring monsters into Earth, they brought over a new way of living. First, some of the creatures on Earth became able to use mana/aura/ energy. Second, inside the gates lay treasures and mana Crystals, and the country which benefited a lot from this was Australia.
