Ten thousand players are locked inside the virtual world of Sword Art Online, unable to log out until someone clears all one hundred floors of the castle Aincrad, where dying in the game kills the player for real. This light novel retells that climb floor by floor from the very first level: the solo swordsman Kirito and Asuna, a rapier user just as set on fighting alone, keep ending up side by side against bosses the original telling passed over.