Feudal Japan, 1543 to 1562. Kansuke Yamamoto is a samurai who dreams of a country united, peaceful from sea to sea. He enters the service of Takeda, the lord of Kai domain. He convinces Takeda to kill the lord of neighboring Suwa and take his wife as a concubine. He then convinces the widow, Princess Yu, to accept this arrangement and to bear Takeda a son. He pledges them his life.