In a flashback, on September 14, 2025, Sinon, who had accidentally fallen down a trap chute while navigating a dungeon below SBC Gurokken in GGO, discovers a boss-class monster and decides to die while trying to defeat it. To her surprise, the position she chose for her attack was out of the monster's attack range, and thus, by conserving her ammo and accurately hitting the boss's weak spot, she is eventually able to defeat it and acquire a new sniper rifle, the PGM Ultima Ratio Hecate II. In the present day, during an ambush on an enemy squadron, Sinon attempts to snipe a target, but he turns out to be a bodyguard named "Behemoth," who overwhelms her squadron with aminigun. When Sinon and Behemoth are the only ones remaining on the battlefield, Sinon manages to shoot Behemoth with her Hecate while falling from the air, earning her victory in the gunfight, despite suffering severe damage to her avatar. Meanwhile, in Alfheim Online, Kirito plans to tell Asuna about something.

As some people are killed within the game Gun Gale Online, Kirito gets back in action, as the murderer may also be a survivor of Sword Art Online