Vivio Takamachi, a Sankt Kaiser royalty of ancient Belka, was previously subjected to mistreatment. Fortunately, she now lives a peaceful life with family and friends while practicing martial arts with her coach, Nove Nakajima. However, Vivio soon becomes the target of the mysterious fighter Heidi E. S. Ingvalt, who demands Nove to reveal the location of the ancient Belkan royals. Refusing to disclose this information, Nove finds herself in a losing battle but Heidi soon falls unconscious. In addition, Nove discovers Heidi's true identity to be a middle school student named Einhald Stratos.