That stone plus something to flatten it with should work fine. You will probably eventually want something coarser to thin the blade, but I suspect that
America in general wastes a ton of food.
Steel shouldn't be an important part of your decision. That said, the easiest thing to sharpen would be a simple carbon.
Also, don't confuse sharpness
A really solid natural medium grit stone. It is a little slow, but leaves a great edge to be refined. Until today
I need a coarse natural, I feel as if the amakusa doesn't do anything