Sonsaku Hakufu

Anime version
The queen of the kingdom of Wu and the eldest sister of the Son Family. Originally set to appear in Shin Koihime Musō, she made her first appearance in the anime. While loving and caring to her sisters and subordinates, she is ruthless in battle and to her enemies. To fulfill the last wishes of her late mother, Sonken, she has led her kingdom into a long war to unite the country. While her methods have been scrutinized, she admittedly accepts responsibility for her actions since she would rather have her hands bloody rather than have her family suffer the same fate as she has. She hopes to abdicate in favor of her sister Sonken and retire with her lover Shuyu after fulling her mother's wishes.

Visual novel version
The queen of the kingdom of Wu, the eldest sister of the Son Family, and leader of the Wu faction in Shin Koihime Musō. If Kazuto joins the Wu kingdom, her tenure as leader is tragically cut short when she is assassinated prior to a battle against forces of the Gi kingdom, subsequently passing the mantle to her sister Sonken, and causing the Go faction to misunderstand that Sō Sō is the one responsible for her assassination.

(Source: Wikipedia)