Name: Shizuka Gozen (静御前)
Birth/ Death: (1165-1211)
Appearance: Book 12 Episode 4
Bio:
She was the daughter of Iso-no-zenji, a famous shirabyōshi at her era, and a beloved mistress of Yoshitsune. She sent out several “secret agents” ("Rokuhara boys" and a servant girl) to inquire about for Yoshitsune. She also helped Yoshitsune to dress in his commander's armor before went marching with his military force.
Notes:
Lady Shizuka appears in a Noh play called Shōzon. In the play, Lady Shizuka dances at a party that Yoshitsune holds for Shōzon. Here is a link to a copy of the Noh play: