Kirito erfährt über Kikuoka von einer Mordserie rund um den Ego-Shooter Gun Gale Online. Der Regierungsbeamte bittet ihn um Mithilfe bei den Ermittlungen.
Nearly a year after the Sword Art Online incident, a new virtual reality MMORPG known as Gun Gale Online has taken Japan by storm. One day, as a top ranked player named Zexceed appears on a streamed broadcast via his avatar, a cloaked man calling himself and his weapon "Death Gun" fires a bullet at Zexceed's avatar through a video screen, causing Zexceed to suddenly convulse and disconnect. A month later, Kazuto Kirigaya is called to meet up with Kikuoka Seijiro of the Ministry of Internal Affairs' Virtual Division, who reveals that Zexceed's user was found dead of acute heart failure a few days after his avatar was shot, also showing evidence of a similar case involving the death of a GGO user. As Kazuto states his doubts that a game could cause someone's heart to fail, Kikuoka, believing Death Gun is specifically targeting professional GGO players, asks Kazuto to once again take up the role of Kirito and investigate what is causing the victims to die. Remembering all the people who died in SAO, Kazuto thinks over his decision whilst spending time with Asuna at the park. Meanwhile, in the world of GGO, a sniper known as Sinon is in top form.
Afin d'identifier le meurtrier qui sévit dans le jeu Gun Gale Online, Kazuto est sollicité par le gouvernement et se retrouve contraint d'enquêter dans ce nouveau monde régi par les armes à feu qu'il n'affectionne que très peu.
Circa un anno dopo l'incidente di SAO, un nuovo gioco, Gun Gale Online, spopola in Giappone. E' principalmente frequentato da giocatori professionisti e un giorno uno di essi sembra essere ucciso nel mondo reale da un giocatore online attraverso un'arma che lui chiama "Death Gun". Kazuto Kirigaya viane quindi contattato da Kikuoka Seijiro della Divisione Virtuale del Ministero degli Affari Interni che gli chiede di iscriversi a GGO per investigare.
《ＳＡＯ》クリアから約１年後。総務省《仮想課》の菊岡から呼び出された和人は、
日本で唯一プロゲーマーが存在する人気のＶＲゲーム《ガンゲイル・オンライン（GGO）》にまつわる、奇妙な事件について聞かされる。
《ＧＧＯ》の有力プレイヤー２名が、《死銃（デス・ガン）》を名乗るプレイヤーにゲーム内で銃撃された後、いずれも謎の死をとげたというのだが……。
많은 희생자를 냈던 소드 아트 온라인 사건으로부터 1년이 지난 지금. 또다시 가상 세계와 관련된 살인 사건이 발생한다. 키쿠오카는 키리토를 불러 게임 내에서의 죽음이 현실의 죽음으로 이어지는 “데스건 사건”에 대해 조사해 달라고 의뢰하는데…
Um ano se passou desde os acontecimentos em ALO. Porém, intrigantes casos de morte surgem e, ao que parece, eles estão relacionados a um MMO...
Un extraño incidente ocurre dentro de un nuevo juego llamado Gun Gale Online, por lo que Kirito volverá a ser llamado para intentar comprender el caso y averiguar lo que ocurrió dentro y fuera de la realidad virtual.
回到現實世界快要滿一年，桐人也逐漸適應現實。這天，他和亞絲娜約在東京的皇居見面，兩人談論著現實與虛擬世界的不同。而在那同時，熱門擬真線上遊戲"Gun Gail Online"中，卻發生了有人在遊戲裡受到槍擊，在現實中也同時心臟衰竭的奇特案件，並且類似的案件有二件。政府"假想課"的課員菊岡調二郎找上了桐人，希望他能潛入"Gun Gail Online"與兇手接觸...
