Cardia is a young girl with poison flowing through her veins that causes imminent death with a single touch. She was whisked away by Arsène Lupin escaping arrest by the Royal Guards after being deemed a monster and a threat to public safety. As her memory only goes back two years, she is desperate to find her father, who may hold the key to what came before.
Due to her lack of experience with the world, Cardia is very unaware of social norms, and is innocent with regards to romance. She is overall a sweet and innocent girl who wants to keep anyone from getting harmed, even those who try to harm her, and she is seen to be in sync with the emotions of those around her. Cardia is also deeply troubled by the fact that she is a Homunculus, and is often conflicted over whether or not her emotions are "real". Her primary struggle, however, is to rid her body of the poison that prevents her from touching others. Due to her condition, she is extremely cautious about human contact, and grows frightened of hurting anyone, especially her loved ones, with her own two hands.
(Source: Code Realize Wikia, edited)