The Sword of Doom

The story follows the life of Ryunosuke Tsukue (Tatsuya Nakadai), an amoral samurai and a master swordsman with an unorthodox style. Ryunosuke is first seen when he kills an elderly Buddhist pilgrim who he finds praying for death. He appears to have no feeling. Later, he kills an opponent in self-defense in a fencing competition that was intended to be non-lethal, but became a duel after he coerced his opponent's wife to have sex with him in exchange for throwing the match and allowing her husband to win. His opponent finds out about the affair prior to the match, and is shown giving his wife a notice of divorce. His rage at Ryunosuke during the match causes him to take an illegal lunging attack after the judge proclaims a draw, and Ryunosuke, the better swordsman, parries and kills him with one stroke of his bokken. Ryunosuke flees town after killing the man, and cuts down many of the dead opponent's clansmen who attack him as he is leaving. His opponent's ex-wife asks to go along with him. To make a living, Ryunosuke joins the Shinsengumi, a sort of semi-official police force made up of rōnin that supports the Tokugawa shogunate through murder and assassinations. Read more on Wikipedia.