Yagyu Sekishusai is a consumate swordsman teaching the Yagyu Shinkage style of fencing from his family dojo. His ambition has always been to achieve fame for the Yagyu clan. His son Munenori hangs around with the local ninja children and frequently avoids practice to do so. As a result, the father considers the son to be weak and is harsh and disparaging both in training and personal life. After Munenori's older brother is injured during the Battle of Sekigahara, Sekishusai decides to name his grandson Hyogonosuke as his successor as head of the Yagyu Shinkage school, considering Munenori to be unworthy of the position. Munenori witnesses his 'mutodori' technique of unarmed combat against a weapon-bearing opponent & then sets out to develop his own style based not on the desire to kill but to defend one's self. He becomes a master in his own right while forming a strong alliance with the Tokugawa who ascend to take power in the land. Munenori becomes a highly-placed key vassal for the Tokugawa, initially as sword instructor & then as Minister of Justice. He also helps to institute the draconian policies of suppression designed to quell any opposition to Tokugawa rule thereby bringing peace to the nation. This viewpoint is not appreciated by his son Yagyu Jubei Mitsuyoshi who is opposed to what he sees as underhanded tactics, regardless of their eventual results 'for the greater good'. Father and son must put aside their differences in order to confront a plot that could de-stabilise the country.