In the series, Japan creates a game that can send people to the second dimension. However, this proves to backfire when it sucks him and a bunch of other nations into its programming, trapping them in the computer. In order to return to their world, they must beat the game.
While training, it is revealed that the Japan in their party is an "error" and an evil duplicate, and that the real Japan has actually remained outside of the computer (though he assists the others from outside the game). America attempts to gather all of the other trapped nations, but the Allies and Axis soon face off against each other. It is revealed that some of the nations have become contaminated with a type of virus. While Germany, Prussia, and Spain are healed, Russia is unable to be cured and is revealed to have been behind the manipulation of the fight, having worked with the evil duplicate of Japan (with Belarus following after him).
The Italy brothers are later revealed to have also been corrupted by the virus, and the other characters must destroy the altar they guard to free them. However, the destruction of the altar only triggers a transformation in the two, who power-up into white robed, "holy" forms and attack the others. Though South Italy is eventually taken out, a still-infected North must be restrained and is nearly killed by a statue. The ghost of Holy Roman Empire intervenes to save him.
The Allies move on to Russia's base to destroy another mind-control artifact, but have to fight both Russia and Belarus. Russia is about to kill America, but Belarus sacrifices herself and reveals that she was secretly working with America to save her brother from the evil Japan. This causes Russia to go catatonic with shock. It is later revealed that Belarus survived the attack, as the evil Japan proceeds to manipulate another nation. Belarus and Liechtenstein journey into Russia's mind and manage to free him from the mind-control, but the evil Japan reveals his newest ally to the other nations: Canada.