Sanrio tenure
Yamaguchi joined Sanrio in 1978.[2] She later rose to become Director and Head of Character Production.[3]
In 1980, Yamaguchi won an internal design contest with her design of Hello Kitty playing the piano, and would become the third primary designer of Hello Kitty.[2]
In addition to her work on Hello Kitty, she served as the designer for the Sanrio characters Dear Daniel and Charmmy Kitty,[3] and has been designing Jewelpet since 2008.[4] She also created the illustration for TV Asahi's official mascot, Go-Chan.[5]
In February 2026, Sanrio announced that Yamaguchi would step down after 46 years as Hello Kitty's designer. She was succeeded by a designer introduced under the pen name Aya. Yamaguchi will remain with Sanrio as an advisor.[6]
