Kai has trained all her life in her father's martial arts school. Though she is looked down upon for being a girl, she proves her courage when assassins launch a ruthless attack on her family. Yet Kai is the inheritor of a dark secret: each month she is transformed into a fox demon, and must hunt and kill a man so she can return to her life as a young woman. As the deaths mount and the townspeople start to voice their suspicions, Kai desperately searches for a way out. Meanwhile, there is a mysterious girl who shares a secret bond with Kai, and whose love may be the key to breaking her curse.