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. She was updated to the VOCALOID4 engine in June 2015. Her voice is provided by the Japanese female singer-songwriter, 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 VOCALOID2 design was unique among the VOCALOIDs. She had no references to YAMAHA based musical instruments and was designed to look cybernetic, giving her a more sci-fi look than most other VOCALOIDs at the time.She generally has a star-theme motif and has a star symbol somewhere in every design for her.
According to information that came from the 2012 redesign, miki was designed to look like she was made out of an inorganic material and was conceptualized as an android. Her body was 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 than she looks, similar to how Hatsune Miku and Kagamine Rincould do the same.
The illustrator also gave an "SFA2 bike" version in 2010 showing miki with her hood up and on a sci-fi themed bike.
Her look was given an overhaul in her VOCALOID4 update and her cybernetic flesh appearance was abandoned. The general science fiction appearance, however, was kept.