SF-A2 codename miki (SF-A2 開発コード miki), is a Japanese VOCALOID developed and distributed by AH-Software Co. Ltd., and was initially released in December 2009 for the VOCALOID2 engine. There is currently ongoing development towards an upgrade to the VOCALOID4 engine. Her voice is provided by the Japanese female singer, Miki Furukawa (フルカワミキ / 古川 美季; Furukawa Miki).
Often shortened to just "SF-A2 miki", her codename of "miki" comes from her provider's name "Miki Furukawa". In Japanese, 'codename' or 'development code' translates as 'kaihatsu koudo'. The meaning of the "SF-A2" part of her name has never been stated.
Her design was unique among the VOCALOIDs. She had no references to YAMAHA based musical instruments like other VOCALOIDs and was designed to look cybernetic.
According to information that came from the 2012 redesign, miki was designed to look like she was made out of a inorganic material and was conceptualized as an android. Her body is designed to look like that of a child, but also give her the overall appearance of a young teenage female. Though she is an android, she is covered in muscles made from various materials such as carbon nanotubes, but were made loose to give a mild deformed look about them. Having an immature-looking body allowed her to appear younger then she looks, similar to how Miku and Rin could do the same.
"Himitsu no Houkago" is a more risque VOCALOID work with an idol atmosphere and a dating sim theme. natsu-P originally uploaded it to Niconico under the username "？？？" due to the song's lewd nature. She has since revealed herself as the producer, and it has since become one of her more notable works.
An album with her singing Christmas songs, "VOCALOIDS☆Ｘ‘MAS", was also set to be released in November 2009. Notable VOCALOID song creators' works are included. She was also used for the introduction to the Hello Kitty game, Hello Kitty to Issho! Block Crash 123! on its official page.
SF-A2 miki was the most popular of the first three AH-Software VOCALOIDs. However, all three were slow to gain popularity and were among the least popular of the Japanese VOCALOIDs for a while. When interviewed, Tomohide Ogata mentioned he had a feeling SF-A2 miki was very popular overseas.
An independent search on Nico Nico Douga revealed that most VOCALOIDs had less then 1,000 videos uploaded on Nico Nico Douga in 2011 between July 1st and December 15th. SF-A2 miki fell into this category.
SF-A2 miki's voice provider, Miki Furukawa, works for Ki/oon records, which is owned by Sony: the same group Utatane Piko's provider, Piko, comes from.