I learned that he held the rope to bind enemies of enlightenment and the sword to cut through the illusionary world, thus revealing ultimate reality.
Also have read somewhere that the rope was to haul the enlightened out of hell and the sword to keep the damned from crawling up, but that maight not be as reliable as some other sources.
Personally, I wouldn't place too much stock in the mystical side of all the Fudo Myo-o/fudoshin thing, as even the japanese see it more as parable than as supernatural reality.
Also, I find the persistent overlay of Buddhist thought on a Shinto-based art a little, um, odd, but hey, whatever floats your boddhisatva ...
