With no knowledge of what synthesizers were, he had trouble in creating the design for a singing computer and it took over a month to complete the commission. His only instructions from Crypton Future Media were to draw an android whose base color scheme would utilize the Yamaha brand synthesizer's blue-green color. In 2007, he created Hatsune Miku's character design which proved immensely popular, both in Japan and abroad.

His doujinshi drew the eyes of the editor of magazine publisher Dengeki Bunko at the time, which resulted in KEI making his debut as an illustrator, with his illustrations being used in the light novel 'Kiseki no Hyougen' (奇蹟の表現) in 2005. Following that, he accompanied a friend who was participating in Comic Market and eventually decided to participate in the event himself. KEI was interested in art since his student days and was interested especially in the artwork of Street Fighter II, Magic Knight Rayearth, and Card Captor Sakura properties. Prior to illustration work, he was a systems engineer. KEI enjoys playing American/imported games on the PC. He is most well known for his creation of the character designs of various Vocaloid characters including Hatsune Miku, Kagamine Rin/Len, and Megurine Luka. He mainly does character design for light novels, but has also contributed to various anime, game, manga, and illustration works.

He was born in Chitose, Hokkaido but now resides in Tokyo. Kei Garou (born April 1, 1981), often stylized as 'KEI', is a Japanese illustrator and manga author.

List of vocaloid artists