Dororo: Season 1, Episode 4

1 - 4: The Story of the Cursed Sword

Dororo and Hyakkimaru come face to face with Tanosuke the Slaughterer, who wields a cursed sword in which a demon dwells. Hyakkimaru narrowly manages to repel Tanosuke, but the demon blade falls into Dororo's hands and begins to take control of him.