Silhouettes for SF-A2 miki, along with the other VOCALOIDs by AHS, were revealed on a poster on November 6th, 2014, however, at the time, it was unconfirmed what they were for.  On November 20th, it was confirmed in the livestream for VOCALOID4 that they all, with the exception of Tohoku Zunko, will be receiving VOCALOID4 voicebanks.
On May 14th, 2015, AH-Software confirmed that miki would only have a Natural voicebank and would release on June 18th, 2015. It is possible to buy her Natural voicebank, but there was also information about a starter pack. Other details such as tempo, range, the prices for her packages were also revealed. It was also shown that miki V4 has an official MMD model by KIO.
On June 4th, a trial version for miki V4 was made available.
As her original package, the performance while singing is soft in lower notes and progressively gets powerful and sharp in higher. While the transition of both singing styles was unstable in the original library, it was improved to make it more natural and smoother.
Improved and more accurate pronunciation and better audio quality.