I was summoned by a goddess to play hero

There are multiple worlds present in the universe, and gods and goddesses compete who will be the supreme divine ruler for each world. To avoid direct battle between the gods that may destroy worlds, a representative battle was develop. Each god chooses his champion from another world and kingdom it represents. whoever unifies the divided kingdom, wins the battle and becomes the supreme divine rulernor god of that world. Champions must come from planet Earth. why Earth? Because Earth is the only planet where people do not show mental breakdown from being transported to another planet. (Probably due to their extensive history of manga, anime or webnovels, everybody on Earth PROBABLY wished to be somewhere else as if they can start all over again and not make the same mistake over again). The story began when goddess Freyah, chose Joe Jackson, to represent him in the game of the gods for the planet known as Evergreen. The planet is young and in comparison with earth, it is around the medieval period. Weapons are magic, swords, clubs, spears, arrows and magical beasts. Freyah was a lesser god, as such, he cannot choose from the top picks of individual who can be summoned from earth. So she chose a champion from a different perspective...