Yui Itsuki is a voice actor, lyricist, and vocalist. She is the co-founder and lead singer of Yousei Teikoku, also known as Das Feenreich. Until 2020, she had been managed by Holy Peak.

She is most often credited as the alias "YUI" for her songwriting. In the Yousei Teikoku mythology, she is credited as "Dictator for Life" (終身独裁官).