>>1975291She was a fake vocaloid created as an April's fool joke on 2ch. She was so popular that no one could let her go. So they made her a utau. Her popularity still grew and she is now considered an honorary vocaloid by Cryton future media. You'll find fan art of her on their web site and she is a dlc for their Project Diva games. Here is a video about her.
http://youtu.be/qucz-rYnnMc 