Kirito is the main protagonist of the Sword Art Online light novel series. His name, Kirito, was taken from his real name Kirigaya Kazuto. "Kiri--" from Kirigaya and "----to" from Kazuto. He was chosen as one of the 1000 beta testers for the Closed Beta of Sword Art Online, the first ever VRMMORPG for the NerveGear.
The first virtual game world, as well as the setting of the first arc of the story, known as SAO for short. The world takes the form of a giant floating castle called Aincrad, with 100 floors in it. Each floor has a medieval-themed setting and a dungeon with a boss, which has to be defeated before players can advance to the next higher floor. Like most RPGs, it implements a level-based system. However, the game is altered in a manner in which players are unable to log out, and if players die in-game, their real life body dies also.