The first of five Musashi series, Shinobu and her brother Genichiro plead with the famous swordsman Musashi Miyamoto to teach them swordsmanship to avenge their fathers death. The killers of their father see the sister and brother practicing with Miyamoto, and so enlist the help of another powerful swordsman, Kojiro Sasaki, which gives Sasaki an excuse to battle Miyamoto.