A year and three months after the War of Underworld, Kirito, Asuna, and Jaymes have begun their mission to usher a new era for both the Human Empire and the Dark Territory. Yet, in the wake of a world where both the empire's goddess and the empire's god have fallen, ancient forces begin to creep, a unforseen plot ensues, and most of a--a mysterious force seeks to spark the divide between worlds...or claim something greater. Kirito, Asuna, and Jaymes, with allies old and new, fight not a war of Underworld, but the War For Underworld.
With three floors under their belt, Kirito, Asuna, Jaymes, and Koharu continue their progression up the lower levels of Aincrad and embark on the Elf War Campaign with their new friend Kizmel. Up ahead lies an oceanic beachfront, a dark and spooky ruin, a floor filled with puzzles, more perilous bosses, more fighting between the DKB and the ALS, and a new party member from Asuna's past. But it's not just the game that's becoming perilous, for there are other players who strive to make the death game their playground...