Ten Duels of Young Shingo: Chapter 1 (1981)

The classic tale of the shogun's illegitimate son Aoi Shingo is told in three parts as he strives to become the greatest fencer in Japan, while his father Shogun Tokugawa Yoshimune seeks to reunite with his lost son.  Part 1 sets up the story and introduces the characters.  When the secrets of Shingo's birth are revealed to him, it sets off a series of events that bring him to cross swords with members of the shogun's inner circle. 

Unfortunately the movie Ten Duels of Young Shingo: Chapter 1 is not yet available on HBO Max.