Cardia is a girl who is referred to as a monster and carries a virulent poison within her body that melts everything she touches. She has lost all memories about herself starting two years ago. She does not show much of a change in her emotions and facial expressions. On the verge of being captured by the English army, she is stolen away by Arséne Lupin. She then begins to work with Lupin and his allies. She has feelings for Lupin for quite some time. At the end of the anime, she and Lupin got married.