Kei Sakurai (櫻井 螢, Sakurai Kei?), also known by her Demon Name The Lion's Heart and Sword: Leonhard August (獅子心剣レオンハルト・アウグスト, Shishi Kokoro KenReonharuto Augusuto?), is one of the main characters in Dies Irae. She is a member of the Longinus Dreizehn Orden, occupying the seat number V in the Black Round Table. She is one of the main heroines of the story and the younger sister of Kai Sakurai.