When Dororo begins, Hyakkimaru’s at his strongest. Without nerves, he cannot feel pain, and without pain, what is there for him to fear? He can jump higher and fall harder than any man because there are no bones in his legs to break.
In many shonen anime, characters like Naruto and Izuku begin at the other end of the scale. Weak and untrained, their stories are about developing strength, yet Hyakkimaru’s is about developing weakness. Isn’t that weird? For each demon he kills, another part of his body is returned, but with that there is a price to pay.