Kirito, Asuna, and Yui stay at a church where the woman Asuna helped earlier, Sasha, looks after children who have become trapped in SAO. Yui recovers from her panic attack, but sadly, Sasha has no information that can help lead to Yui's parents.
An Army player named Yulier appears. She apologizes for the conduct of the soldiers from the previous day, and asks Kirito for help: the Army had become corrupt as a result of the influence of Kibaou, the player who first called Kirito a "beater" and since became the vice-leader of the Army. Kibaou was also responsible for sending the group of Army players to fight the Gleam Eyes, a fight that resulted in massive casualties, including the party's leader Kobatz. The leaders of the guild were ready to expel Kibaou, but Kibaou managed to trap the Army's leader, Thinker, in a dungeon located beneath the first floor.
Kirito and Asuna are suspicious of the story, thinking there may be a trap. Yui, however, states that Yulier is telling the truth. Thus, they decide to defer to Yui's judgment and help her.
The dungeon, which Kibaou had hoped to use for his own benefit, has many powerful high-level monsters lurking about, which Kirito is able to fend off. Just when they find Thinker in a safe area, however, the group is attacked by the Fatal Scythe, a powerful boss monster suited for floor 90 and higher.
As Yulier and Thinker teleport out of the dungeon using a nearby GM console, Yui suddenly summons a massive flaming sword and fells the Fatal Scythe in a single stroke. She reveals that she's not a player, or even human: she is an artificial intelligence, originally created to counsel players who were under great stress. When the Death Game started, however, she was locked out of the game by the core AI, Cardinal. Unable to interact with players, she was forced to watch as players fell into despair. She, too, fell into despair, until she saw Kirito and Asuna, two players who found a way to be happy in spite of their circumstances, and decided to approach them.
Unfortunately, due to her interfering with the game, Cardinal would see her as a "foreign object" within the game and would delete her. Kirito, however, is able to use the GM console to keep the game from deleting her completely: he saves her programming and memories as an in-game object, "Yui's Heart", which he stores in the local memory of his NerveGear in the hopes that he can one day restore her.