Death Gun's apparent ability to kill real people by shooting their avatars draws Kazuto Kirigaya into an official investigation of Gun Gale Online. Only a year has passed since his escape from Sword Art Online, and he has been readjusting to life outside the game. Now, he returns to his Kirito persona and enters another virtual world to stop a suspected murderer.
In Gun Gale Online, Kirito meets Sinon, an accomplished sniper troubled by a traumatic past. Their pursuit leads them to enter the Bullet of Bullets tournament, where Death Gun is certain to appear. Neither knows the true extent of their opponent's powers, and wounds from the past complicate their efforts. With further deaths to prevent—and the possibility that either of them could become a victim—Kirito and Sinon must confront a threat that reaches beyond the game.
