Crypton Future Media intended to produce a VOCALOID with a young teen girl's voice at first following Hatsune Miku, but there was also demand for a boy's voice, so Crypton Future Media hired a voice actress who could produce both.
Kagamine Rin was the first voicebank developed and introduced to the VOCALOID consumer market on November 8, 2007. However, the package included two voicebanks: one for Rin and another for Len both provided by the seiyū Asami Shimoda, Kagamine Len was unveiled after Kagamine Rin on December 3, 2007.