Sword art online. Volume 2 / Progressive.
(Book)

Having cleared the first and second floors of Aincrad at great cost, Kirito, Asuna, and the rest of the players ascend to the third floor. Tenuous new allies await them--most crucially, Kizmel, the elven knight. Kizmel is supposed to be a minor NPC with low-level AI, but she soon reveals herself to be much more. With new allies come new complications, though, and the elves of the vast third-floor forest are no more united than the players who have just arrived there. The intrigue deepens when a mysterious figures challenges Kirito, and what begins as a simple contest of skill may actually be something far deadlier.

Ages 13 & up.

Translated from the Japanese.