Excelling socially and academically, Asuna Yuuki is on track to ace her high school entrance exams. Her friend and classmate, Misumi "Mito" Tozawa, advises her to take a short break from studying and join her on the launch day of Sword Art Online (SAO)—the highly anticipated online virtual reality multiplayer game. Asuna accepts her offer and soon meets her in the game.

In a cruel twist of fate, Asuna, Mito, and every other player logged into SAO find themselves trapped in the game permanently. The only way out is to clear all one hundred floors of the game, and to make matters worse, dying inside the game will kill the player in real life. With SAO now turned into a nightmare death trap, Asuna and other gamers—such as the lone swordsman Kazuto "Kirito" Kirigaya—must adapt and survive, all whilst attempting to beat the unforgiving competition to the top.