Anime version
The Blonde Queen of the kingdom of Wei and a General of the Kan empire. Sōsō likes beautiful women and likes to tease her subordinates, especially her strategist Jun'iku, but is also attracted to Kan'u. (In fact, a famous scene in the first season's closing credits shows her "kidnapping" a dining Kan'u and then kissing her while inside a private bedchamber. Kan'u was later returned to the dining table with the rest of her friends, albeit covered in kiss marks and quite shaken.) A brilliant ruler and military genius, she also isn't afraid to speak her mind in any situation if she doesn't like it. Despite being seen as a little cruel and calculating, she is in reality an honorable person. Sousou also doesn't like beind denied what she wants, and vows to get Kan'u in her bedchamber.
In Shin Koihime Musō, she is also revealed to be an excellent chef.

Visual Novel Version
The ruler of the Gi kingdom. She rarely becomes upset and wishes to obtain beautiful females into her control, particularly Kan'u. In the first game after becoming a captive of the Shoku kingdom, she strongly questions and is annoyed by how Kazuto could still be alive due to his lack of leadership and his naiveness. In the sequel, she is a brilliant and powerful warlord with the objective of reuniting China under her rule, and makes use of Kazuto's knowledge of Asian history to her advantage if he becomes her advisor.

(wikipedia.org)