Trama

Kirito uncovers a conspiracy within Ordinal Scale, a popular AR game developed for a new system called The Augma.

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, and soon Kirito decides to join them. However, they're about to find out that Ordinal Scale isn't all fun and games.

In the year 2026, the Augma is released to the public as an alternative system to the AmuSphere, as it projects a game layer on top of reality while the player is conscious, rather than using FullDive. The most prominent combat-based game is Ordinal Scale, in which a player's abilities are ranked by ordinal numbers. Due to this new technology, more and more people have been using the Augma, rather than VR technology.

Asuna, Lisbeth and Silica while in a cafe encourage Kirito to play OS upon hearing that Aincrad bosses have appeared. Although, Kirito himself has no interest in the Augma or Ordinal Scale, but nonetheless agrees to join Asuna in a boss fight. Kirito joins Asuna and Klein in a boss fight against Kagachi the Samurai Lord at Akihabara, where the game's mascot, AI idol singer Yuna, appears and gives players buff effects as she sings. Kirito fails to achieve anything due to his lack of real world physical strength and agility. Eiji, the number-two ranked player, aids the group in defeating the boss. Before Asuna makes the killing blow, Eiji whispers the word "Switch," a game mechanic from SAO that she recognizes. Asuna is given a kiss and some bonus points for contributing the most by Yuna herself.

The next night, Asuna joins Klein and his group for another boss fight at Yoyogi Park while waiting for their last group member, unaware that he was injured by Eiji the night before. Asuna leaves Klein and his guild behind and proceeds to the fight against the Storm Griffin, which is again presided over by Yuna. Klein and his guild are surprised by the sudden appearance of a second boss, Zanghi the Flame Caller, and shockingly supported by Eiji, who physically attacks and defeats Klein and his entire guild in the real world using superior reflexes and seemingly superhuman strength. Eiji then proceeds to allow the boss to attack Klein, leaving him terrified. When Asuna returns to where she left them, Klein and his guild are nowhere to be seen. The following morning, as Kirito practices with OS in Yoyogi Park, a girl he doesn't know appears in a white hood, mouths something wordlessly and points off into the distance before disappearing. A confused Kirito is surprised by Asuna who has arrived to have lunch with him. While eating together, Asuna reveals that a player resembling Eiji was a former member of the Knights of the Blood Oath named Nautilus and believes them to be the same person, while Yui deduces that the spawn locations of the Aincrad bosses line up with the SAO dungeon maps. Noting the absence of Klein, Kirito tries to check up on him.

Asuna, Lisbeth and Silica join the boss fight against Strict Hermit at Yebisu Garden Place, where Yuna and Eiji appear again. At the same time, Agil contacts Kirito and tells him that Klein has been hospitalized with a broken arm; Kirito, alarmed, rushes to protect Asuna and their friends. During the boss battle, a second boss, Dorz'l the Chaos Drake, suddenly appears and fixates on Silica. Eiji blocks Silica's escape by intentionally pushing her into the path of a lethal boss attack, and Asuna is defeated while protecting her; an orange orb materializes from Asuna's Augma and is quickly collected by one of the OS drones. Kirito arrives and enraged for what Eiji did to Silica and Asuna attempts to attack him but is pushed back, Eiji tells him that he needs to rank up and grow stronger before they fight. After the battle, while sleeping Asuna begins to suffer memory loss, and reveals to Kirito that her memories of SAO had disappeared and accompanies her to the hospital for examination.

Asuna learns that the Augma device scanned her brain specifically for her SAO memories and that the memory loss could worsen. Her doctor also reveals that other former SAO players using the Augma have experienced the same phenomena. While sitting in the waiting room, Asuna suddenly mimics the gesture for activating the player menu, before suddenly collapsing. Kirito takes Asuna to Aincrad in ALO (Alfheim Online) to help her hopefully regain her memories by reminding her of what they did together in SAO, but to no avail. They return to their cabin on floor 22 and after seeing Asuna breaking down in tears, Kirito resolves himself to help her regain her memories. Kirito visits Klein in the hospital and confirms that Klein's SAO memories are also missing. Kirito goes to the Dire Tusk boss battle at Tokyo Dome City looking for Eiji, where he is joined by Sinon; although he is concerned for her safety, Sinon reminds Kirito that she is not an SAO survivor. During the boss battle, an SAO survivor is defeated and Kirito witnesses a glowing memory orb being collected by an OS drone. Yui tries to follow the memory orb into the drone but fails after being blocked by the OS system. After the battle, Kirito is frustrated that Eiji did not show up, but meets the hooded girl a third time, who repeats her actions from before. Kirito and Yui manage to figure out that she is pointing towards Touto Technical University.

Kirito goes to the university and meets Professor Tetsuhiro Shigemura, who developed the Augma. Shigemura refuses to answer any questions. Before leaving, Kirito notices on Shigemura's desk a picture of a girl who resembles Yuna. Kirito talks to Seijiro Kikuoka, who informs him that Shigemura's daughter, Yuna, died in SAO. Kirito warns Kikuoka that the memory loss may be affecting other SAO survivors playing OS. Visiting Asuna's home, Kirito promises Asuna that he will get her memories back. While searching for clues, Kirito encounters the hooded girl yet again, who he confirms is Yuna. When she tells him his rank is too low, Kirito decides to level up hardcore, and recklessly chain-solos as many bosses as he can, and improving his AR sword-work with help from his sister, Leafa. Eventually, at one particular boss fight he manages to increases his rank in the single digits, where he also encounters Eiji; who tells him to meet him at the Tokyo National Stadium for the final event.

Days later, the OS players gather at the Tokyo National Stadium for Yuna's first live concert. In the underground parking lot, Kirito duels with Eiji, who claims he has a way to return Asuna's memories. During the duel, Eiji reveals that he and Yuna had gotten close in SAO and he could only watch as she died right in front of him. Kirito manages to defeat him by damaging the technology he was using to boost his strength and agility, however Eiji reveals that Shigemura has been harvesting memories of SAO players in an attempt to reconstruct his lost daughter's soul and resurrect her as an AI; having SAO survivors concentrated in one place is the final stage of the plan and Eiji believes he has won. After Kirito leaves, Eiji informs Professor Shigemura of his defeat and is suddenly double-crossed by him as he has the most amount of memories of Yuna and summons a boss to defeat him and take his memories. Kirito rushes back upstairs to warn everyone, calling Kikuoka on the way. Kikuoka warns Kirito that all the memory harvesting drones scanning everyone at once could damage the players' brains, killing them like the NerveGear did in SAO.

As a horde of Aincrad bosses appear and terrorize the stadium, Kirito and Yuna join the battle. Yuna tells Kirito that the Augma has a hidden full-dive feature and he can use it to defeat SAO's 100th floor boss to stop the scan and save everyone. Before diving, Kirito gives Asuna a promise ring. Entering the Ruby Palace of Floor 100, Kirito, Lisbeth, Silica, Agil, and Sinon confront the boss. They are easily overwhelmed until Asuna, Leafa, Klein, and several other memorable players from ALO and GGO come to their aid. Yui restores their saved abilities from SAO, together they manage to overwhelm the boss. Asuna along with Yuuki's spirit attack the boss with her original sword skill "Mother's Rosario" and Kirito finishes it off with his signature dual blades sword skill "Starburst Stream". The voice of Akihiko Kayaba congratulates them on their victory and gives Kirito an extremely powerful sword as a reward.

The group returns to the arena still in full-dive where Kirito, now OS's top-ranked player, effortlessly dispatches the bosses with his new sword, halting the scan and saving the other players. Meanwhile, in the real world, Kikuoka finds Shigemura in the abandoned server room of Argus (the defunct company that once ran SAO) and arrests him, but not before Yuna's spirit bids him farewell. The hooded Yuna restores the survivors' memories and fades out of existence since her existence was tied to that of the Floor 100 boss. Afterwards, Leafa, Silica, Lisbeth, Sinon, Klein, and Agil are shown at his bar watching the news, revealing that the number of people using the Augma had drastically decreased and the number of people using VR tech had increased as a result.

Meanwhile, Kirito and Asuna fulfill the promise they made to each other in Aincrad, to watch a meteor shower together in the real world. Asuna returns Kirito's promise ring, allowing him to properly place it on her finger.

In a post-credits scene, Kikuoka, who was impressed with Shigemura's attempt at AI and soul reconstruction, recruits Shigemura to Rath for Project Alicization. (Courtesy of Wikipedia)