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.
Crypton Future Media
Due to the success of placing a character on the box art of Meiko, the concept was carried over to her successor Kaito and later Vocaloids to encourage creativity, however neither Vocaloid's box art originally had the intention to represent that Vocaloid. Though Meiko experienced good sales, Kaito was the only one who initially failed commercially, causing less demand for male voices for a while after Kaito's initial release. However, sales eventually picked up and Kaito later won the Nico Nico Douga second best seller award of 2008. Meiko and Kaito are reported to be in discussion for an update. Several updated vocal expressions have already been recorded for Kaito.
In April 2011, it was confirmed six vocal expressions had been recorded for Kaito, two of which were dropped and the remaining four were being brought forward with one having reached alpha stage already. The Character Vocal (Hatsune Miku, Kagamine Rin/Len and Megurine Luka) series Appends had been created from vocal performances of their voice providers, however the new Kaito Appends were created by adding echo, force and tension to the samples.