Fullmetal Alchemist: Brotherhood, Dororo Recommendations
What makes someone human? This is the question that lies central to these two shows. Both series involve a main protagonist on a quest to reclaim their body and meanwhile discovering what humanity is. Also both are able to produce sword(s) from their arm(s) and are quite capable of fighting, although their styles are different.
As a result of a forbidden ritual, main character looses part(s) of his body and now he is on the quest to reclaim it.