Okay, my understanding is that the Nakayama are real hard jnats like an Ozuku but of course I am not sure if they are considered "ultra hard". Out of these stones, the Nakayama Asagi, Ozuku Asagi and a Shoubudani, which one the hardest stone and best to use for a base stone with a nagura?
I was told that I would just need one ultra hard nagura that would work any any of the stones listed above so trying to find one! Thanks for the help!