Millerna Sara Aston is the third princess of the kingdom of Asturia, the youngest daughter of King Grava Aston and Queen Therese Aston. Her eldest sister Marlene is deceased, and her second sister Eries forced her to abandon her medical studies, which had been a personal ambition to become a doctor. Millerna is initially deeply infatuated with the knight Allen Schezar, though she is betrothed to the wealthy merchant prince Dryden Fassa. Uncomfortable with the restrictions of royal life and her arranged engagement, Millerna runs away from Asturia to join Van Fanel's group, seeking to fulfill her dreams and gain independence. Her primary motivation is a desire for personal freedom and to be valued for who she is, not merely for her royal status. Throughout the series, she gradually comes to appreciate Dryden's good qualities, though they ultimately separate on good terms when Dryden says he will return when he is more deserving of her. This prompts Millerna to realize she cannot depend on others for her happiness. Her role in the story is as a supporting character who provides emotional support to the main cast, especially to Hitomi Kanzaki, and uses her medical knowledge to aid the group. She is a skilled healer with expertise in medical operations. Key relationships include her unrequited love for Allen, her evolving bond with Dryden from reluctant fiancée to mutual respect, and her friendship with Hitomi and Van. Her development moves from a sheltered princess longing for romance to a more self-reliant woman who understands her own worth. While she has no combat abilities, her medical skills and her determination to defy her family's expectations to pursue her own path are her notable attributes.