Yui Itsuki is a Japanese voice actress and musician from Nagoya, Aichi Prefecture, born on October 25. After graduating from the Nagoya branch of the Japan Narration Acting Institute, she made her professional debut in 2003. Her first major role was Moe Mizukoshi in the anime series D.C. ~Da Capo~, a character she would reprise in subsequent adaptations and related games. This early work helped establish her presence in the industry.

Throughout the 2000s, Itsuki built a career with a variety of supporting roles in anime. Notable performances from this period include Kira Sakurazuki in the Futakoi series, Miya Suzuki in My-HiME and its sequel Mai-Otome, and Megumi in Magical Pokaan. In 2008, she voiced two of the characters mentioned in the query: Mio Osakabe in Kanokon: The Girl Who Cried Fox and Paula in the first season of Black Butler. Her association with the Black Butler franchise would become a recurring thread in her filmography, as she later returned to voice Paula in Black Butler II and, much later, in Black Butler: Public School Arc in 2024. Her career in video games includes roles such as Yoshiko Anzu in the Arcana Heart fighting game series and Rui Nakane in the visual novel True Tears.

Alongside her voice acting, Itsuki has maintained a significant parallel career as a musician. She is the lead vocalist and a founding member of the gothic metal band Yōsei Teikoku, where she performs under the persona of Dictator for Life. With the band, she has performed numerous anime theme songs and has been involved in songwriting, often credited as YUI. She is also the vocalist for the electronic music project Denkishiki Karen Ongaku Shuudan, using the alias Karen.

Her career has included affiliations with several talent agencies. She began with I'm Enterprise, moved to Holy Peak in late 2008, and has been signed with Office Restart, an agency established by fellow voice actress Ami Koshimizu, since April 2022. Beyond acting and music, she is known for her technical hobbies, including building her own personal computers, and has also expanded into activities as a VTuber.