Kirito

Kazuto Kirigaya never asked to have his memory taken away. Unfortunately, he was given no choice in the matter. As a mortal human stuck in a camp for demigods with nothing but his wits, a mental case goddess, and a Stygian iron blade to guide him, he finds himself in a world not his own. Now he must either complete his destiny, or allow darkness to take the life he can't remember. (Book 1 in the Sword Art Olympian fan-fic)