Sword Art Online the Movie: Ordinal Scale

Asuna loses her memories because Professor Tetsuhiro Shigemura designed the Augma device to secretly scan and extract the SAO survivor memories. He uses these extracted memories to reconstruct the digital soul of his deceased daughter Yuna. During the battles in Ordinal Scale, Asuna's memories are harvested by the OS drones that collect orange orbs from players who fall in combat.

Earlier in the film, doctors reveal that the Augma device had scanned Asuna's brain for specific SAO memories, causing her memory loss.

Yuna is an AI idol and mascot of Ordinal Scale, but she is actually an artificial intelligence created from the extracted memories of Professor Shigemura's daughter, who died inside SAO. The real Yuna perished in the SAO virtual world, and her father created the AI Yuna hoping to revive her digital soul and reunite it with her physical body.

Kirito notices a photograph on Shigemura's desk of a woman who strikingly resembles Yuna, hinting at their connection.

Eiji is the second-ranked OS player who initially helps Kirito and his friends. His true motivation is to assist Shigemura's plan to extract SAO memories because he wants to help restore Yuna, the AI version of Shigemura's daughter. Eiji believes Shigemura's work can bring Yuna back to life. However, he ultimately helps Kirito stop the plan when he realizes the danger it poses to all SAO survivors.

Eiji whispers "Switch" during the first boss battle, a nostalgic phrase from SAO, hinting at his deeper connection to the original game.

The Augma device scans players' brains during combat in Ordinal Scale. When players are defeated in the game, OS drones collect orange memory orbs that contain their SAO memories. Shigemura programmed the system to extract these memories without the players' knowledge, using them to reconstruct his daughter's digital consciousness.

Kirito witnesses an OS drone collecting a radiant memory orb from a fallen SAO survivor during the Dire Tusk battle.

Klein disappears and loses his SAO memories because he falls in battle during the OS game, making him a victim of Shigemura's memory extraction scheme. Like Asuna, his memories are harvested by the OS drones when he is defeated, causing him to forget his experiences in SAO.

Agil messages Kirito urgently about Klein falling prey to a strange malady, leaving him seriously injured.

When Eiji whispers "Switch" during the boss fight against Kagachi in Akihabara, he is using a nostalgic phrase from SAO that signals to his partner that they are about to switch positions or take over the battle. This detail hints at Eiji's deeper connection to SAO and his history as a former player.

This phrase appears early in the film but its significance is revealed later when Eiji's true motives are uncovered.

Kirito defeats the 100th floor boss of Aincrad with help from his allies. Yui restores their SAO abilities, allowing Kirito and his team, including Asuna, Leafa, Klein, Lisbeth, Silica, Agil, and Sinon, to use their original SAO skills. After a difficult battle, they emerge victorious, and Akihiko Kayaba congratulates Kirito, gifting him an extraordinary sword.

Yuna reveals to Kirito an undisclosed full-dive feature in the Augma that could help him conquer the 100th floor boss.

Yuna sacrifices herself after helping Kirito and the others defeat the 100th floor boss and stop Shigemura's plan. Her existence as an AI was tied to the memory extraction system, and once the system is shut down, she fades away. However, before disappearing, she restores the memories of all SAO survivors, undoing the harm caused by Shigemura's scheme.

Yuna tells Kirito that his current skills are insufficient, setting him on the training path that leads to the final battle.

The Aincrad bosses appearing in Ordinal Scale are part of Shigemura's memory extraction scheme. Yui discovers that the boss locations in OS align with the dungeon maps from SAO. Shigemura uses these familiar bosses to lure SAO survivors into playing Ordinal Scale, where their memories can be harvested. The bosses are also deployed during the stadium chaos to prevent players from escaping the memory scanning.

Asuna, Lisbeth, and Silica urge Kirito to join OS because of rumors about Aincrad bosses appearing in the game.

Professor Shigemura extracts SAO survivor memories to reconstruct his daughter's digital soul. His daughter Yuna died inside SAO, and he believes that by gathering enough SAO memories, he can recreate her consciousness as an AI and eventually reunite it with her physical body. This is why he created both the Augma technology and the AI Yuna.

The mysterious hooded figure (Yuna) guides Kirito to Touto Technical University, where Shigemura works.

Akihiko Kayaba appears as a voice after Kirito defeats the 100th floor boss of Aincrad inside the game. He congratulates Kirito on his achievement and gifts him an extraordinary sword as recognition. This appearance is significant because Kayaba was the creator and admin of the original SAO, and his acknowledgment affirms Kirito's status as the ultimate champion.

Kayaba's presence is hinted at throughout the film through references to SAO and the original game's creator.

In the post-credits scene, Seijirō Kikuoka is shown being recruited by Shigemura into his clandestine organization called Rath. This suggests that despite being arrested, Shigemura continues his work on artificial intelligence and soul reconstruction, and Kikuoka becomes involved in these mysterious endeavors, setting up potential future stories.

Kikuoka expresses interest in Shigemura's bold endeavors in AI and soul reconstruction during their conversations.