Kasane Teto is a character originally created as a fake "Vocaloid."
Following the rising popularity of Hatsune Miku, which was released in August 2007, vip@2ch users collectively planned the troll "new Vocaloid release" for the April Fool's day of 2008. Fake demos were posted on Nicovideo, Sen providing the illustration, and Mayo Oyamano the voice.
After the troll, Mayo's voice was recorded for the fanmade voice synthesis program UTAU, which was released just before a month. Soon many composers started to create songs using this newcomer, and Teto established popularity both on Nicovideo and YouTube.
Kasane Teto is not a "fake" diva any longer. The popularity led to 3D models, figurines and many illustrations by fans. Furthermore, the regular update of the voicebank and UTAU platform has made Teto one of the most famous counterparts to Vocaloid characters.
