Mizuki Yamaguchi is a Japanese voice actress born on December 23 and a native of Ibaraki Prefecture. She stands 155cm tall and her skills include kendo, in which she holds a shodan rank, and playing the piano. Her hobbies include reading, and she holds a Level 3 certification in business proficiency. She previously worked under the agency futurum LLC and currently works as a freelancer. She is also known under the alias Yuika for her work in adult games.

Yamaguchi's anime voice acting credits include roles in several television series. She voiced Jenny, Tornado, and other characters in the anime Iron Kid. She also voiced roles such as Sofia and Jenny in My Giant Friend. Outside of anime, she has provided voices for foreign drama dubs, including the role of a young Lucas and Melinda in Hospital of the Dead.

In the field of video games, her roles include Rain in the arcade game Dodonpachi Dai-Fukkatsu. She worked on Nintendo 3DS titles such as Charapet: Tsukutte! Sodatete! Character Shougakkou, where she voiced Hanausa and Coffee Capybara, and Oshaberi Usagi: Oshare Collection, in which she voiced the protagonist and provided narration. Other game credits include Gensou Senki, X.A.O.C, End of Eternity, Magia Break, and Princess Field. She is also known for voicing Kiyoka Irisu and Mifuyu Sakurai from The Fruit of Grisaia.

Her work in voice dramas includes roles in the Classmate series and the Kaiki Hirokatsu no Kaiki En series. She also worked as an assistant and in short dramas for the FM Setagaya radio program Talk Hippopotamus, and served as a personality for the Tokyo Net Radio program MaMiAyu Town. Additional credits include toy voice work for Ossan! Button! 3.