The protagonist of the tale is a young boy named Kazuto Kirito Kirigaya who plays Sword Art Online, a massively multiplayer online role-playing game.
Unlike computer games, this one involves the use of a high-tech helmet that immerses the player in the SAO universe. Players are beginning to notice a flaw, though, after starting the game: there is no option to log out in the menu. As a result, no player can escape the virtual reality and is stuck in the fantasy realm.
The game's creator, who also forewarns in the introduction that violently removing the helmet from the outside would result in the player's death, appears to be the perpetrator. Additionally, it is said that when a player dies in-game, electrical currents from his helmet, which are actually merely intended to transport data to his brain, kill him. The players must succeed in reaching the game's final level and winning it in order to leave.
