Kenji Misumi's Trilogy of the Sword

The son of an executioner and the assassin he loved yet murdered learns of his origins, leaving his foster parents to avenge his mother's death.

The Sword (Ken?) is a 1964 Japanese film directed by Kenji Misumi. From a screenplay by Kazuro Funabashi, based upon the short story Ken (Sword) by Yukio Mishima. The story is centered on Kokubu Jiro (Raizo Ichikawa), a prominent member of his university's Kendo dojo.

Hanpei is a gentle young samurai who loves flowers. But one day he witnesses an old mans quick draw of the sword. He is so impressed that he becomes the old mans pupil. Soon Hanpeis skill of sword comes to attention of his lord. The lord orders him to assassinate a man...