This is a posable action figure from the Nendoroid series.
From Good Smile Company:
From the anime series Dororo comes a Nendoroid of the character whose body parts were stolen by 12 demons, Hyakkimaru! He comes with three face plates including his standard expression, an "unsheathed" expression with his prosthetic arm in his mouth from when he unsheathes his swords and an intimidating combat expression.
For optional parts, he comes with sword arm parts and prosthetic arm parts for each arm as well as his cloak for long travels. Be sure to add him to your collection!