A year after escaping Sword Art Online, Kazuto Kirigaya has been settling back into the real world. However, his peace is short-lived as a new incident occurs in a game called Gun Gale Online, where a player by the name of Death Gun appears to be killing people in the real world by shooting them in-game. Approached by officials to assist in investigating the murders, Kazuto assumes his persona of Kirito once again and logs into Gun Gale Online, intent on stopping the killer. Once inside, Kirito meets Sinon, a highly skilled sniper afflicted by a traumatic past. She is soon dragged in his chase after Death Gun, and together they enter the Bullet of Bullets, a tournament where their target is sure to appear. Uncertain of Death Gun's real powers, Kirito and Sinon race to stop him before he has the chance to claim another life. Not everything goes smoothly, however, as scars from the past impede their progress. In a high-stakes game where the next victim could easily be one of them, Kirito puts his life on the line in the virtual world once more.

The story is set a couple of years after the events of Sword Art Online, where Kazuto Kirito Kirigaya and his sister Suguha meet up with Asuna Yuuki, Rika Lisbeth Shinozaki, and Keiko Silica Ayano at the SAO Survivor School. Kirito then attends emergency counseling, while the girls go for a swim at the pool. It turns out that said emergency counseling is a subterfuge set up by Seijirou Kikuoka, aiming to rehash the incident of Sword Art Online in hopes of determining Akihiko Kayaba's motives. What will the girls get up to in the pool, and what awaits Kirito and his counseling?

Excelling socially and academically, Asuna Yuuki is on track to ace her high school entrance exams. Her friend and classmate, Misumi Mito Tozawa, advises her to take a short break from studying and join her on the launch day of Sword Art Online (SAO)—the highly anticipated online virtual reality multiplayer game. Asuna accepts her offer and soon meets her in the game. In a cruel twist of fate, Asuna, Mito, and every other player logged into SAO find themselves trapped in the game permanently. The only way out is to clear all one hundred floors of the game, and to make matters worse, dying inside the game will kill the player in real life. With SAO now turned into a nightmare death trap, Asuna and other gamers—such as the lone swordsman Kazuto Kirito Kirigaya—must adapt and survive, all whilst attempting to beat the unforgiving competition to the top.

In 2026, four years after the infamous Sword Art Online incident, a revolutionary new form of technology has emerged: the Augma, a device that utilizes an Augmented Reality system. Unlike the Virtual Reality of the NerveGear and the Amusphere, it is perfectly safe and allows players to use it while they are conscious, creating an instant hit on the market. The most popular application for the Augma is the game Ordinal Scale, which immerses players in a fantasy role-playing game with player rankings and rewards. Following the new craze, Kirito's friends dive into the game, and despite his reservations about the system, Kirito eventually joins them. While at first it appears to be just fun and games, they soon find out that the game is not all that it seems...