One year after escaping Sword Art Online, Kirito is asked to investigate a series of mysterious deaths linked to Gun Gale Online, a virtual-reality game focused primarily on firearms. A player known as Death Gun claims to be able to kill his opponents in the real world by shooting them inside the game. To uncover his identity, Kirito enters the Bullet of Bullets tournament and meets Sinon, a skilled sniper trying to overcome a trauma connected to guns. Forced to work together, they confront an enemy whose actions reopen wounds from their past and raise new questions about the safety of virtual worlds.