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.
Kizuna AI
Kizuna is able to livestream and record videos in a virtual environment; this is generally considered to rely on the free software MikuMikuDance. After the production crew designs a 3D model, they manually control the model to make certain movements. Then, they hire a voice actor to give the animation a voice. MikuMikuDance has often been used in the videos of Vocaloid pop music, allowing users to import and control the 3D models of virtual characters such as Hatsune Miku.