A year has passed since SAO was cleared. Summoned by Kikuoka of the Virtual Division at the Ministry of Internal Affairs and Communications, Kazuto learns of a series of bizarre murders linked to the popular VR game, Gun Gale Online (GGO), the only game in Japan played by pros.

Armed with a large sniper rifle, Hecate II, the young girl Sinon is making a name for herself as the No. 1 sniper in GGO. When her squadron ambushes another squadron, she succeeds in taking out her first target. But when she takes aim at her second target, a robed “Behemoth,” he dodges the bullet.

In real life, the player Sinon is a high school student named Shino Asada. On her way home from school, she’s dragged into an alley by delinquent girls. Their leader, Endo, tries to extort money from Shino, but she bravely refuses.

Kikuoka has recruited Kirito to investigate GGO, and so he logs in. To lure Death Gun into targeting him, he hopes to enter Bullet of Bullets (BoB), a tournament to decide the most powerful gunman in GGO. But as a first-timer, he doesn't know his way around this game, and soon loses his way, when he catches sight of Sinon and approaches her.

To register for BoB, Kirito starts entering the required information into a terminal, but is astounded to see that the form includes columns for his real-world name and address. He is temporarily torn when he realizes that without this info, he won't be eligible for the top prizes...

A man in a beat-up cloak watches Kirito fight his first battle and demands to know if he's "the real thing". The man has the tattoo of Laughing Coffin, a murderer's guild that existed within SAO. He tells Kirito that he'll kill him someday, and vanishes.

Kirito decides that Death Gun and the man in the cape will be appearing in BoB. He uses the remaining time to exchange information with Sinon and find out more about the contestants. Sinon sees how strange he was acting during the qualifier and asks him what happened. She learns that he is a SAO survivor. The main BoB tournament begins and 30 players are dropped in a 10km wide field.

The man in the cape shoots Pale Rider and he is eliminated despite the fact that he has HP remaining. The man says that he is Death Gun, and declares that he will bring true death. Asuna and her friends are watching a live stream of BoB and realize that Death Gun is one of the leaders of Laughing Coffin.

Sinon is attacked from behind by Death Gun and paralyzed. He's using a Black Star Type-54, ironically the same gun that Sinon used to shoot the robber. Her memories of the incident come flooding back and Sinon loses control, and Death Gun tries to kill her to make Kirito angry. But just before he can kill her Kirito saves her at the last second. Sinon is out of the fight, and Kirito tries to flee with her but is pursued by Death Gun.

After escaping from Death Gun, Kirito and Sinon lay low in a desert cave. There, Kirito speculates on how Death Gun murdered other players. In doing so, he hits upon a certain terrifying possibility.

BoB nears its end, and the only surviving players are Kirito, Sinon, and Dark Wind, the second place winner of the last tournament. Since Death Gun may have multiple partners, and Dark Wind may be in danger as well, Kirito decides to defeat him first. He acts as a decoy while Sinon snipes the enemy. Kirito's trust in her pays off as her bullet strikes true, and he finally faces off with Death Gun.

Death Gun's attack is modeled after Star Splash, a SAO skill that doesn't exist in GGO. Death Gun is skilled with not only a gun but a blade as well, and he gradually wears down Kirito's health. Meanwhile, Sinon's scope has been destroyed by Death Gun and she cannot attack, so she's forced to simply watch the fight. She grits her teeth and wonders if there's anything else she can do.

Kyouji attacks Shino, saying he'll kill himself after she's dead. Kazuto saves her at the last second by jumping Kyouji. During the fight, Kazuto is hit with Kyouji's poison syringe, but miraculously it doesn't work and Kirito is saved. The next day Kazuto and Shino go to meet Kikuoka, and discuss the incident. Kikuoka has a message from one of the captured Death Guns...

It's reported that the Holy Sword Excalibur has been discovered inside ALO. Hearing the news, Kirito and Leafa decide to take possession of Excalibur before other players get to it first.

Kirito and the others are tasked with subjugating the Frost King Thrymr, and a quest to recover Excalibur. It's Yui's guess that this isn't a quest planned by the game admins, but something automatically generated by the system. And if that's the case…

Kirito and the others are taking on Thrymr, the Boss lurking at the bottom level of the dungeon. But unable to make much of a dent in Thrymr's HP, they soon find themselves in grave danger. Just then, their new ally, Freyja, raises her voice…

In an upcoming update of ALO, Floors 21-30 of New Aincrad will be unlocked. Asuna, Kirito and Yui revisit their dream of once again living together in their log cabin on Floor 22.

Hearing rumors about a brilliant player known as Zekken, Asuna decides to mount a challenge. But when Asuna logs out, she is told by her mother to take an exam to transfer into an academically oriented high school.

Asuna is asked to help the guild “Sleeping Knights,” which has decided to disband soon due to the members’ circumstances. Before they do, they want to defeat a Floor Boss with only their party.

Asuna and the Sleeping Knights’ attempt to defeat the boss on Floor 27 has been observed by a guild specializing in boss raids. Now 20 of its members block the boss room. With Kirito stalling the rest of the guild, can Asuna and the others break through?

A few days have passed since Yuuki suddenly disappeared from in front of Asuna, and she still hasn’t logged in to ALO. Later, Asuna meets Kazuto on the school roof, where he hands her a note and tells her Yuuki might be at the location written on it.

As a tester for the world’s first medical-use Full-Dive device, Yuuki has been diving into virtual worlds from the hospital. Unable to leave her hospital room, she longs to go to school again. To make that wish come true, Asuna asks Kazuto for help…

Getting to experience the outside world, Yuuki’s days are more satisfactory than ever before. In ALO, the players have a barbecue and end up on a quest. In the real world, Asuna and the girls take a trip to Kyoto. One day, Asuna receives an email…