Kirigaya Kazuto, born as Narusaka Kazuto, and known as Kirito in «Sword Art Online» (SAO), «ALfheim Online» (ALO), «Gun Gale Online» (GGO), «Project Alicization», and Unital Ring, is the protagonist of the main Sword Art Online series.

Kirito was chosen to be one of the one thousand beta testers for the closed beta of Sword Art Online, the first ever Virtual Reality Massively Multiplayer Online Role-Playing Game (VRMMORPG) for the NerveGear, and later joined the official version of the game. He thus became one of the 10,000 players who were trapped in Sword Art Online, where he remained a solo player for the majority of the game, willingly taking on the role of a Beater to reduce discrimination against other former beta testers, as well as actively taking part in Boss battles as one of the Clearers.