Sword Art Online Progressive Volume 4 (ソードアート・オンライン プログレッシブ 004, Sōdo Āto Onrain Puroguresshibu 004 Sword Art Online Progressive Volume 4?) is the fourth installment in the "Progressive" series, a reboot of the original Sword Art Online light novel series written by Kawahara Reki. This volume covers the events that took place while clearing the 5th Floor of Aincrad. It was released on December 10, 2015.