In order to search for Yui's guardians, Kirito and Asuna set off for the Town of Beginnings.
When they hear that Thinker, a leader of The Army, has been left trapped in a dungeon, they take on the job of rescuing him.
Along with Yulier, who sought their help, and Yui, who insisted on tagging along, Kirito and Asuna descend to the underground dungeon on the first floor.
There, an unexpected enemy awaits them.
Realizing that he has no chance against this enemy, Kirito tries to let the others escape, but...