* Based on Kawahara Reki's light novel series Sword Art Online.

In 2022, the world of virtual reality was upended by the arrival of a new invention from a genius programmer, Kayaba Akihiko. Called NerveGear, it was the first full-dive system and with it, came endless possibilities to VRMMORPGs.
In 2026, a new machine called the Augma is developed to compete against the NerveGear and its successor, the Amusphere. A next-gen wearable device, the Augma doesn't have a full-dive function like its predecessors. Instead, it uses Augmented Reality (AR) to get players into the game. It is safe, user-friendly and lets users play while they are conscious, making it an instant hit on the market. The most popular game on the system is Ordinal Scale (aka: OS), an ARMMORPG developed exclusively for the Augma.
Asuna and the gang have already been playing OS for a while, by the time Kirito decides to join them. They're about to find out that Ordinal Scale isn't all fun and games...

Source: aniplexusa

In the season finale, Asuna, Yuuki as well as all of their friends continue to live happily in the world of Alfheim and New Aincrad. From duels and quests to taking bosses head on, the group is determined to make the most of their time together, by any means. However, when Asuna receives urgent news of Yuuki's condition, the line between her two worlds will become thinner than ever. And she will learn how the human spirit, as well as the love which sustains it, transcends all life.

Yuuki lives out her dream. Asuna begins to repair her broken relationship with her mother.

After the Sleeping Knights guild disbands Asuna sets out to find Zekken (Yuuki), who reveals her tragic story.

Asuna and Sleeping Knights prepare to raid the 27th Floor Boss, but have to take out a rival guild blocking their way.

Zekken, leader of the Sleeping Knights guild wants to defeat a powerful floor boss. Needing a seventh Asuna agrees to join them.

Asuna has a confrontation with her mother about her current schooling, and goes on to duel Zekken.

After hearing that a new update from New Year's Eve opens up floors 21-30 of new Aincrad, Kirito and the others race to reach floor 22 with the hope of once again purchasing the home he shared with Asuna and Yui.

After clearing the first two stages the ice giant of the third stage proves more than the group can handle. Freyja tells Kirito the secret to defeating him.

At the entrance to Thrymheim, Yui explains that the quest they were given was created by the Cardinal System's Automatic Quest Generation Function and that if they did not succeed in their quest, a final war event, Ragnarok, would be triggered. Sometime later, at the end of the second floor of Thrymheimr, the group encounters two minotaurs, and they are forced to rely on Sword Skills that could deal elemental damage to them in addition to physical damage, but also leave the player rigid for a few seconds after the skill is used up. With Kirito revealing his new technique of using consecutive Sword Skills with each of his swords to avoid the period of rigidity, they are able to defeat the two minotaurs. Later, after defeating the boss guarding the entrance to the lowest floor of the castle, they encounter an NPC woman trapped in an ice cage along the way. Although the others insist that it is a trap and plan to avoid her, Klein ignores their advice and frees the woman, who was revealed to be Freyja. Instead of running away, Freyja asks to join the group and Kirito reluctantly agrees to the request. After preparing for the final battle by recharging their buffs, the group enters the throne room, where they met the king of the frost giants, Thrym.

Kirito returns to ALO, bringing Asada with him, in order to obtain the sword, Excalibur.

The Bullet of Bullets tournament comes to a close. Sinon confronts her inner demons.

With Kirito is losing to Death Gun, Sinon looks for a way to save him.

With the Bullet of Bullets tournament coming to a close, Kirito and Sinon set a trap for Death Gun, but another player might jeopardize it.

As Kirito and Sinon lay low in a desert cave, Kirito ponders on how Death Gun murdered the other players.

Sinon is attacked from outta nowhere by Death Gun. Luckily Kirito manages to rescue her, but they are pursued by Death Gun.

Kirito and Sinon hunt Death Gun through the Bullet of Bullets tournament. Asuna realizes the danger Kirito is in and sets out to find answers.

Certain that Death Gun is competing in the BoB final, Kirito approaches Sinon beforehand about exchanging information, and begins to investigate the new players in the tournament.

Suguha confronts Kazuto about his activities in the online world as he grapples with having killed people in the Sword Art Online incident.

After witnessing Kirito's win in his first preliminary match, Death Gun asks Kirito if he is the real deal. Before he can answer Kirito notices his tattoo of Laughing Coffin and wonders if he's run into him before.

To bait out Death Gun, Kirito enters Bullet of Bullets, a tournament to decide the most powerful gunman in GGO.

As some people are killed within the game Gun Gale Online, Kirito gets back in action, as the murderer may also be a survivor of Sword Art Online

In real life, Sinon is afraid of the sight of guns because of a robbery gone bad. Kirito tells Asuna he plans to log into Gun Gal Online.

In a flashback, on September 14, 2025, Sinon, who had accidentally fallen down a trap chute while navigating a dungeon below SBC Gurokken in GGO, discovers a boss-class monster and decides to die while trying to defeat it. To her surprise, the position she chose for her attack was out of the monster's attack range, and thus, by conserving her ammo and accurately hitting the boss's weak spot, she is eventually able to defeat it and acquire a new sniper rifle, the PGM Ultima Ratio Hecate II. In the present day, during an ambush on an enemy squadron, Sinon attempts to snipe a target, but he turns out to be a bodyguard named "Behemoth," who overwhelms her squadron with aminigun. When Sinon and Behemoth are the only ones remaining on the battlefield, Sinon manages to shoot Behemoth with her Hecate while falling from the air, earning her victory in the gunfight, despite suffering severe damage to her avatar. Meanwhile, in Alfheim Online, Kirito plans to tell Asuna about something.

2 years after the events of sword art online, Kirito is approached by a government agent with a new proposition after the apparent murder of pro players of the new main stream MMO Gun Gale Online.