Sou Youki

Sou Youki (蒼 遙姫, Sō‎ Yō‎ki) was the younger sister of Sou Gen, the first emperor of Saiunkoku. As the first High Priestess of Saiunkoku, she is the founder of the Hyou Clan, beginning the tradition of the clan being ruled by women.

Appearance
Youki was said to be a beautiful princess. She had long lavender hair which was cut in a princess style in the front. She was often dressed in a priestess' attire. She wielded two fans.

Plot
During the founding of Saiunkoku, she along with her brother worked to drive off the evil entities with the help of the Eight Immortal Sages. When the mirror where they sealed the demons shattered, she played her erhu to pacify them and seal them away in each great lakes of the country.

After Sou Gen became the emperor, she made a contract with her brother to handle all the supernatural events that will occur in the future while he ruled the country. Thus, Sou Gen conquered the highest peak in Saiunkoku, the Banri Mountain range and gave it to her. She established the manor of the Hyou clan there and became the head and the High Priestess to lead the clan. She dedicated her life solely to protect Saiunkoku from all supernatural disasters. Thousands of years later, when Ruka was held in the prison of time, a priestess in white robe appeared carrying a red umbrella. It is possible that the priestess was actually Sou Youki herself, protecting the High Priestess candidates.

Erhu
She was very gifted with the erhu. Her playing could even calm the raging spirits. Thus, the Hyou clan's traditional instrument became the erhu.

Supernatural powers
She also possessed a lot of supernatural powers typical of a High Priestess of the Hyou clan. Her power was so great that she could stabilize the Hyou Clan's domain in the Banri mountain with her power alone at the time of its foundation as there wasn't many magicians around at that time.

Sou Gen
Sou Gen was her brother and the first emperor of Saiunkoku. She worked together with him many times to stabilize Saiunkoku and build it up as a nation.

Black Immortal
It was mentioned in the novel that the Black Immortal was in love with her. Even now, the Immortal occasionally helps human in hopes of being able to meet Sou Youki again. Whether she was aware of this or not is unknown.