Kaai Yuki

Voice Provider: Anonymous (elementary school student at time of release)

Developer: AH-Software Co. Ltd.

Engine: Vocaloid 2 (2009), Vocaloid 4 (2015)

Release Date: December 2009

Kaai Yuki stands out in Vocaloid history as the first female voice bank created entirely from a child's voice samples. Her vocals come from a fourth grader, which meant her identity had to stay completely private for legal protection. That young voice provider has only spoken publicly twice about the character—once for Yuki's 10th anniversary in 2019 and again for Vocaloid's 20th in 2024—but she's never been identified.

When Yuki got her Vocaloid 4 update in October 2015, AH-Software brought in a second voice provider specifically to record growl samples, since the original provider's voice had naturally matured over the years. It's a practical solution that let them keep Yuki's signature sound intact while adapting to real-world changes.