Millerna Sara Aston is the third princess of the kingdom of Asturia. She is the youngest daughter of King Grava Aston and Queen Therese Aston, with two older sisters: the eldest, Marlene, who died before the events of the series, and the second, Eries. Millerna was originally studying to become a doctor, a pursuit she was passionate about, but was forced to abandon her medical studies by her sister Eries. Prior to the main story, she becomes betrothed to the merchant prince Dryden Fassa as part of a political arrangement. Millerna is intelligent, independent, and strong-willed, though she maintains a polite and well-mannered demeanor appropriate to her royal status. She is deeply compassionate and desires to help others, which drives her ambition to practice medicine. At the start of the series, she harbors a strong romantic attachment to the knight Allen Schezar, but her feelings are not reciprocated in the same way. This unrequited love initially causes her some jealousy toward Hitomi Kanzaki, but she eventually grows to become a close and loyal friend to Hitomi. Millerna's role in the story becomes active when she defies her father and the political alliance between Asturia and the Zaibach Empire, choosing to run away and join Van Fanel, Hitomi, Allen, and their companions in their struggle against Zaibach. She brings her medical skills to the group, often tending to wounds and providing care. Over the course of the series, Millerna undergoes significant personal development. She begins as a princess constrained by familial duty and her romantic fantasies about Allen, but she learns to assert her own will and independence. Her relationship with Dryden evolves from initial resentment to mutual respect and affection; at the end of the series they part on good terms, with Dryden stating he will return when he is more deserving of her. Millerna comes to realize that she cannot rely on others to define her happiness and must forge her own path. Her notable abilities are primarily in the field of medicine: despite her young age, she is a skilled practitioner of medical operations and healing arts, knowledge she uses to support her allies throughout the conflict.