Young Chizuru Yukimura sets out on a mission to find her disappeared father, who is a medical doctor named Koudou. She disguises herself as a boy and heads to Kyoto, only to discover that the city is perilous. While strolling around the streets, she is attacked by two ronin, but to her surprise, a red-eyed and white-haired samurai slays them instantly before he is taken out by three men from the Shinsengumi, a special police unit that serves the shogun.