In the year 2022, the Virtual Reality Massively Multiplayer Online Role-Playing Game (VRMMORPG), Sword Art Online (SAO), is released. With the Nerve Gear, a virtual reality 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, 2022, all the players log in for the first time, and subsequently discover that they are unable to log out. They are then informed by Kayaba Akihiko, the creator of SAO, that if they wish to be free, they must reach the 100th floor of the game's tower and defeat the final boss. However, if their avatars die in-game, their bodies will also die in the real world. The story follows Kirito, a skilled player who is determined to beat the game. As the game progresses for two years, Kirito eventually befriends a female player named Asuna with whom he ultimately falls in love. After the duo discover the identity of Kayaba's avatar in SAO, they confront and defeat him, freeing themselves and the other players from the game.
Upon returning to the real world, Kirito learns that Asuna and 300 other SAO players have still not awakened yet. Following a clue about Asuna's whereabouts in another VRMMORPG called Alfheim Online (ALO), Kirito also logs in there. Helped by his sister Suguha, known as Leafa in the game, he learns that the trapped players in ALO are part of a plan devised by Nobuyuki Sugō to perform illegal experiments on their minds to put them under his control, including Asuna, whom he intends to marry in the real world in order to take over her family's company. After Kirito stops Nobuyuki's plans, he finally reunites with Asuna in the real world.
Soon after, Kirito plays another game called Gun Gale Online (GGO) to investigate the mysterious connection between it and deaths occurring in the real world. Assisted by a female player he meets in the game called Sinon, he identifies and exposes the culprits, who include some former members of a murderous guild he had previously encountered in SAO.
Kirito is later recruited to assist in the development of a state-of-the-art game, UnderWorld (UW), which has an interface that is far more realistic and complex than the previous games he had played. In UW, the flow of time proceeds a thousand times faster than in the real world. However, he ends up falling into a trap set by one of the murderers from GGO and wakes up inside the game, unable to log out, with his real self left in a comatose state. Eventually he starts to question if he is the real Kirito or an artificial intelligence modeled after him.

Voiced by: Yoshitsugu Matsuoka (Japanese), Bryce Papenbrook.





  Kazuto, who uses the portmanteau "Kirito" as his character name, is a "solo" player who has been branded a "beater" (a combination of beta tester and cheater) by the players in Sword Art Online. When Kayaba announces that the players of Sword Art Online can no longer log-out without clearing the game, he quickly overcomes the shock. He power-levels to improve his odds of survival in the game, and emerges as a frontline floor-clearer known as the Black Swordsman (黒の剣士 Kuro no Kenshi?). In SAO, he is the sole «Dual Blades» skill user. During his time in SAO, he falls in love with a female player, Asuna, and even marries her in-game.
After the end of the Sword Art Online incident, 300 people have yet to wake up, including Asuna. He receives a picture from another VRMMORPG called Alfheim Online in which Asuna could be seen in a cage on the legendary World Tree, which no Alfheim player has ever reached directly. Kirito decides to get a copy of the game and rescue Asuna nonetheless. Shortly after joining Alfheim, he befriends another player called "Leafa" (who is actually his cousin Suguha). Leafa helps Kirito grasp the game and offers to help him reach the World Tree. After a long journey and many adventures, Kirito manages to reach the World Tree and overcomes its obstacles to reach the top. He rescues Asuna and discovers Leafa's true identity. As ALO and SAO share the same game engine, among other features, a bug allows Kirito to retain most of the skills and money he obtained in SAO upon playing ALO with the same Nerve Gear, already beginning his journey with an advantage over other players. Despite this, he ends up being forced to discard all of his items (except the one containing Yui, which reformats itself as a navigation pixie), as they were not recognized by the system.
He is later asked to register in Gun Gale Online in order to investigate real life murders that are somehow linked with assassinations in-game. It is soon revealed that the murders are committed by ex-players from Sword Art Online, who were part of a player killing group known as Laughing Coffin. His actions result in the capture of two out of the three culprits. The last member escapes and is not heard of until the events of volume 9, and is responsible for an attempted murder of Kazuto.
In the Alicization Arc, he has been assisting in the development of the fourth generation full dive interface, Soul Translator, by testing its thought acceleration functions. However, he has no memory of what he has been doing as a result of his memories being suppressed, voluntarily, by the system. He is attacked and poisoned by Johnny Black (The third culprit who escapes) in the real world and wakes up in Underworld with no memory of the game or how he got there. He meets up with Eugeo and helps him out of some tough situations, during which he partially remembers his time with Eugeo and Alice during his "childhood" in Underworld. He then decides to aid Eugeo in finding Alice while he searches for a way out, back to reality.
In the real world, he lives with his mother, Midori, and younger sister, Suguha, in a family of three. In fact, he was actually adopted by Mr. Minetaka Kirigaya and Mrs. Midori Kirigaya when he was just a year old, due to his real mother and father passing away after an accident. His real mother was actually Midori's sister, meaning his adopted mother is also his aunt. However, Kazuto did not know this until he discovered the truth at the age of ten, and Suguha, being in fact the Midori's own daughter, was also unaware of Kazuto's adoption and is in actuality his cousin.



Voiced by: Ayana Taketatsu (Japanese), Cassandra Morris.





    Suguha, alias Leafa, is Kirito's younger cousin in the real world. She is a diligent worker and has been practicing Kendo for 8 years. Kirito/Kazuto calls her "Sugu". After Kazuto gets trapped in Sword Art Online, she begins playing Alfheim Online in an attempt to understand him better. She develops feelings for Kazuto after she learns that he is not really her brother, but understands that his feelings for Asuna are too strong. Coincidentally, she meets Kazuto's avatar, Kirito, in Alfheim and aids him in his search for Asuna, unaware of Kirito's true identity. After understanding the depth of Kazuto's love for Asuna, she resolves to give up on him and instead becomes attached to Kirito in ALO, but later is heartbroken when she finds out that Kazuto and Kirito are one and the same. Nevertheless, she pulls herself together and aids Kirito in rescuing Asuna.