Board Thread:Questions and Answers/@comment-29003089-20160711212152/@comment-6697950-20160711213007

Nearly every VRMMO game in the series randomly generates avatar appearance. In most games, all you can choose is your name, race and maybe modify your hairstyle later on. Asuka Empire might be the only known game with more customisation options, but even then it apparently doesn't allow full control over avatar customisation.

In-universe-wise, Kirito just happened to get a very rare avatar. Though this of course has use for the story too. Kirito wouldn't have become acquainted with Sinon if he looked like a guy.