In 2022, thousands of players log into the new virtual-reality game Sword Art Online and discover that they are unable to log out. Its creator then announces that their only chance of returning to the real world is to clear all one hundred floors of the enormous floating castle of Aincrad. Because dying in the game also means dying in reality, every battle becomes a matter of survival. Kirito, one of the former beta testers, initially chooses to progress alone before growing closer to Asuna and other players. Through exploration, boss battles, and the bonds formed within this artificial world, he searches for a way to free everyone trapped inside.