Kaai Yuki (歌愛ユキ) is a Japanese VOCALOID developed and distributed by AH-Software Co. Ltd., and was initially 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 were not produced from an adult.
She was updated to the VOCALOID4 engine in October 2015 and used a new voice provider for the growl components. This was due to her initial provider maturing, 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.