ArFA-Sys

Afasys (アファシス, Afashisu?), alternatively spelled as ArFA-Sys in Western localisations, is an original Sword Art Online game character and the Protagonist's personal companion in Sword Art Online: Fatal Bullet. Afasys is a rare type, modeled Type-X, of an Artificial Intelligence (AI) companion called the Artificial Financial Adviser System and her full ID is Afa System Type-X A290-00.[citation needed] Due to Afasys only allowing the Protagonist to use Afasys's official name, the companion was nicknamed as Rei (零, Rei?, lit. "Zero") by Leafa in reference to the zeros appended to her Unit ID.