In 2022, a Virtual Reality Massively Multiplayer Online Role-Playing Game (VRMMORPG) called Sword Art Online (SAO) is released. With the NerveGear, a helmet that stimulates the user's five senses via their brain, players can experience and control their in-game characters with their minds. On November 6, 10,000 players log into the SAO's mainframe for the first time and discover that they are unable to log-out. They are then informed by Akihiko Kayaba, the creator of SAO and NerveGear, that if they wish to be free, they must reach the 100th floor of the game's castle and defeat the final boss. Additionally, in-game death or removal of the NerveGear out-of-game is designed to cause the microwave emitters in the device to kill the players. One of the players is Kazuto "Kirito" Kirigaya, one of the 1,000 beta testers in the game's previous closed beta. With the advantage of previous VR gaming experience and a drive to protect other beta testers from discrimination he isolates himself from the greater group and plays the game alone, bearing the mantle of "beater", or "beta cheater". As the players progress through the game Kirito eventually befriends a young girl named Asuna Yuki, forming a relationship with and later marrying her in-game. After the duo discover the identity of Kayaba's program Heathcliff in SAO, who was discovered to be the leader of the guild Asuna joined in, they confront and destroy him, freeing themselves and the other players from the game.