Emirun and Rex knew each other outside the game; inside Sword Art Online, where dying means dying for real, they meet again by chance and join a scouting party. A player killer called the Black Swordsman wipes that party out in front of them. Shaken, the two track down Asuna, the rapier prodigy whose name every floor knows, and beg her to train them for what lies ahead. This film ties into the game Echoes of Aincrad.