A new virtual reality game known as "Gun Gale Online" (GGO) is promoted via streamed broadcast, featuring top-ranked player named XeXeeD. In a bar, a cloaked man nicknamed "Death Gun" fires a bullet from his pistol through the video screen, causing XeXeeD to suddenly convulse and disconnect. A month later, Kazuto Kirigaya and Asuna Yuuki hang out at a park, discussing the differences between the real and virtual worlds. Four hours earlier, Kazuto meets with Seijirō Kikuoka, a member of the Virtual Division of the Ministry of Internal Affairs and Communications, who reveals that Tamotsu Shigemura, real-life persona of XeXeeD, died of acute heart failure a few days after his avatar was shot by Death Guns army. Kikuoka, believing that Death Gun is specifically targeting professional Gun Gale Online players, begs Kazuto to once again take up the role of "Kirito" and investigate the situation. In the present, Kazuto and Asuna talk about how the vertical structure of Aincrad in "Sword Art Online" (SAO) represents the axis of time and the plane of space.