There is an interesting analogy between Musashi and the 羅刹(rasetsu), rakshasa in the translation. They are born from Brahma’s foot, and they are shape changers. The foot part seems ironical right now, once Musashi is a cripple at the moment. On the other hand, he really changes his “shape” when that “demon” appears and urges to fight. Ittosai, called Musashi a demon, but he himsefl is a good one as well (and he’s using a Hanmi, a foot technique). Section 4 of Gishaku says that the title of the demon king Nirrti is the great Raksasa. He holds a sword and has a ferocious appearance. He has a double-edged sword in his right hand, and makes the sign of double-edge sword mudra (ritual gesture) in his left hand. Since Ittosai is hiding his right arm, this really makes sense.