A possible concise summary is:
Kirito and Asuna, two players trapped in a virtual reality game called Sword Art Online, impulsively get married after having sex. They find a mysterious girl named Yui, who claims to be their daughter, but is actually an AI that monitors the mental health of the players. Yui helps them rescue Thinker, the leader of a rebel faction, from a trap set by Kibaou, a power-hungry tyrant. Yui reveals her true identity and is targeted for deletion by the system, but Kirito manages to save her data as an item. Kirito and Asuna admit that they got married too quickly, but decide to stay together anyway.
Some possible facts that can be extracted from the text are:
- 1. Asuna and Kirito are married in the game Sword Art Online.
- 2. Yui is an Artificial Intelligence that pretends to be their daughter.
- 3. Heathcliff is the leader of the Aincrad Liberation Front and the final boss of the game.
- 4. Kibaou is a rival player who traps Thinker, the second-in-command of the ALF, in a secret dungeon.
- 5. Yui saves Asuna and Kirito from a powerful monster called the Fatal Scythe and reveals her true identity.
- 6. Kirito manages to save Yui's data as an in-game item before she is deleted by the system.
- 7. Yulier is Thinker's lover and seeks Asuna and Kirito's help to rescue him.
- 8. Sasha is the owner of an orphanage on the first floor where Asuna and Kirito stay with Yui.