Sword Art Online Progressive 9 (Light Novel) - Reki Kawahara

In clearing the seventh floor, Kirito transforms into a Civis Nocte, kindred to vampires, receiving great power in exchange for a lethal weakness to sunlight. Together with Asuna and Kizmel, he pursues the Fallen Elves who have stolen the five scared keys at the center of the Elf War questline. To the group's surprise, however, their search ends up taking them back to the fourth floor. While there, Kirito and company accept a request from Lavik, the former Commander of the Sandalwood Knights Brigade, becoming embroiled in an ancient dispute between the elven peoples and delving into the past of Viscount Yofilis. Amid all this drama, one thing is for certain: No one can call the NPC characters simple AI anymore!