Sword Art Online: Hollow Realization

After the battle against the raid boss and receiving an attack from the dark elves, a familiar figure appears before Kirito after: the dark elf swordsman from Sword Art Online, Kizmel! Kirito is also in an event area that should be devoted to rescuing the captured Silica and Premiere, but danger approaches the dark elves in the form of an evil demon...

(Source: Yen Press)

Note: Sword Art Online: Hollow Realization is an adaptation of the console game of the same title.