The mysterious group that attacked the Ocean Turtle turns out to be a secret unit under orders from the U.S. National Security Agency. And its leader, Gabriel, has battled Kirito and Sinon before.

Shasta, commander of the Dark Territory's dark knights, had intended to use Administrator's death as a chance for peace with the Human Empire. But his plans are thwarted by Emperor Vecta's return to the land of darkness.

Alice and Asuna head to the World’s End Altar as Kirito confronts Gabriel. Unless he can defeat Gabriel and return to the real world before the maximum-acceleration phase begins, Kirito will have to spend the next 200 years in the Underworld.