Sword Art Online: Hollow Realization Vol. 2 (manga)

After a harmless dungeon-crawling adventure with Premiere escalates into a high-level battle called the "Ground Quest," Kirito discovers remnants of the floating castle of Aincrad-a world that should have been destroyed long ago. Determined to find more clues to the puzzle and uncover Premiere's identity, Kirito decides to delve deeper into this mysterious quest...Just where could it all lead?