Hatsune Miku
Hatsune Miku was the first Vocaloid developed by Crypton Future Media after they handled the release of the Yamaha vocal Meiko and Kaito. The name of "Hatsune Miku" was conceived soon after the Vocaloid 2 announcements, when an English and Japanese vocal were developed for the character. The intended design was delayed and later used for Megurine Luka instead. Miku was intended to be the first of a series of Vocaloids called the ""Character Vocal Series"", which included Kagamine Rin/Len and Megurine Luka. Each had a particular concept and vocal direction.
SF-A2 Miki
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, giving her a more sci-fi look than most other Vocaloids at the time. 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 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 than she looks, similar to how Hatsune Miku and Kagamine Rin could do the same.