There once was a man named Gold Rodger, a pirate, and he was given the glorious title: ‘King of the Pirates’ for possessing the legendary treasure, One Piece. He had fame, fortune, and power, until one day, he caught and brought to the execution tower to be executed.

The story begins with Yggdrasil, a popular online game which is quietly shut down one day; however, the protagonist Momonga decides to not log out. Momonga is then transformed into the image of a skeleton as "the most powerful wizard.

In August of 20XX, a portal to a parallel world, known as the "Gate," suddenly appeared in Ginza, Tokyo. Monsters and troops poured out of the portal, turning the shopping district into a bloody inferno.