Sword Art Online, Vol. 23 (light Novel)

As Kirito, Asuna, and Alice brave the wilds of the mysterious VRMMO Unital Ring, Sinon's introduction to the world is equally harrowing. After numerous setbacks, she finds herself without friends or equipment--and barely any thirst points left to her name. Backed against a wall, she'll need to defeat a terrifying boss monster to survive. Meanwhile, Kirito's group splits up in order to search for Sinon and defend their home, unaware that a mysterious assailant lies in wait.