Youko was a 16-year-old living a fairly ordinary life as an honor student in Japan, whose primary worry is her naturally red hair. One day at school, a man named Keiki suddenly appeared and bowed at her feet, swearing loyalty to her. The school was then attacked by a giant bird, and she reluctantly accepted his protection. He gave her a sword and transports her and two of her classmates to the kingdom of Kou.
She eventually learned that she was the heir to the throne of the kingdom of Kei, and although she was initially reluctant, she accepted the position through her growth in the story. Among the obstacles she faced were the king of Kou, who used her classmate Sugimoto in his effort to stop her from attaining the throne. In a later story arc, as the newly appointed queen, Youko learned of several problems in her kingdom, including a revolt in the province of Wa. Her nickname is "Sekishi" ("red child"), after her bright red hair.
Despite being a weak character to begin with, appearing very withdrawn and not wanting to do anything that would bring attention to herself; Youko eventually grows throughout the episodes (especially seen in episode 5). She grows in strength and maturity, becomes empathetic towards the people around her, thinking articulately about her actions (especially as queen) and continues to do so through towards the end of the series.
Some queens are benevolent while others are malicious and they tend to rule in the absence of a king. Even when a king is present, sometimes the queen can be the true power behind the throne. Whatever the case, any queen worth her merit is a powerful mix of beauty, power, and resolve.