Three Kingdoms counterpart: Xiahou Yuan
Birthday: April 19
Horoscope: Aries
Age: 18
Height: 170 cm
Blood Type: A
Three Sizes: B-90 W-59 H-89
School: Kyousho's College, 2nd Year
Toushi Rank: A-Rank
Weapon: Jade Shot

Manga
A female assassin Sousou once saved, earning her total loyalty. She is extremely skilled, even more so than Ryofu (however this may have been due to Ryofu's illness had reached its final stages at the time they fought), very durable to the point of seemingly not feeling any pain and specializes in pressure point attacks. She uses a jade shot attached to a very long metal wire as a projectile and for restraining her foes. She develops a deep respect for Chou-un when they fought each other. Chou-un recognises that Myosai is fighting for someone who is very important in her life (Sousou). Myosai attacks her own allies when they catch Ryubi, claiming that she wanted to capture Ryubi herself. She was stabbed from behind by one of Sousou's toushi. Chou-un defeated the toushi and ordered him to bring Myosai back to Kyosho safely.

Anime
Same as in the manga, in the anime it is revealed that Sousou found her years ago in the war zone in a jungle somewhere presumably in South East Asia. Myosai was dressed in army fatigues suggesting she was a rebel or revolutionary of some sort. She was nearly raped by a soldier (she isn't wearing pants and her underwear has been pulled down). The soldier is shown with a bullet wound in his back. Either Myousai killed him herself or Sousou did to save her (he is not shown holding any weapons but Myousai is holding a gun). Sousou is dressed as a tourist and it is presumed that he took her back to Japan with him. Myosai was defeated by Ryomou & Saji in the Battle of Chibi. She was also the only Kyosho member whose fate was not revealed in the anime's ending. It is revealed in Ikki Tousen Great Guardians Episode 5 that she is in fact still alive and seems to be working with the mystery girl. In episode 6, Myosai is working with Saji and used to distract Kakouton while Saij made of with Ryofu. As she was about to finish Kakouton, she was interrupted by Hakufu. In the end, Myosai was defeated by Kakouton. She again fights with Kakouton and Koukin, only to be interrupted by Sou Sou's return. She returns to Kyosho with Kakouton and Sou Sou.

(Source: Wikipedia)