Kayaba Akihiko

is the development director and GM of «Sword Art Online». He is also the designer of the Nerve Gear and the VR Seed. He is the mastermind behind Japan's largest net crime, «the Sword Art Online Incident».

Heathcliff
Heathcliff is the leader of what is considered to be the «Sword Art Online»'s strongest guild «Knights of Blood». He is the owner of the «Unique Skill» «Holy Sword» and is considered to be strongest player in-game. He also was able to hold off the boss of the fiftieth level for ten minutes by himself, which earned him the title of legend.

After SAO
He reappears to help Kirito defeat Noboyuki Sugou, and leave Kirito with the Seed. He also stated he tried to copy his mind onto the virtual network so as to be a fully realized being of SAO.