Kaai Yuki (歌愛ユキ) is a Japanese VOCALOID developed and distributed by AH-Software Co. Ltd., and was initially released in was released in December 2009 for the VOCALOID2 engine. Yuki's vocals are based on an elementary school student. With her voice provider being a young girl the identity of her provider has never been revealed for legal reasons. She was the first female VOCALOID whose voice samples are not produced from an adult.
There is currently ongoing development upgrade to the VOCALOID4 engine, this uses a new voice provider. This was due to the fact her provider had matured, making re-sampling problematic.
Yuki is meant to be portrayed as a 9 year old elementary school student. She is said to be "As tall as 10 big apples" and "As heavy as 86 apples". Her red randoseru is a motif of YAMAHA's wind controller, WX5.
Yuki and Kiyoteru were announced in November 2009. Interestingly, at the end of the previous month Crypton Future Media had just made their own announcement of a series called Project if..., which was set in an elementary school setting.