The original question being:
"Do I need a stone to follow a (high quality) Nakayama"
can be answered with a no.

As already stated Nakayama is a mine that produces very high quality polishing stones.
MaruKa/MaruIchi is a stamp on a particular stone given by the owner of the mine,
labeling the stone as of high quality.

So a genuine Nakayama Maruka is of very high quality
but still not necessarily perfectly fine for the use with razors!

You will need someone with very much experience that handpicks a stone for you. Maybe one with a stamp saying "kamisori" wich translates into "razor".

I would not search on my own for a suitable hone but ask one of the friendly
but very busy guys like SO and Yamashita if they can recommend you one.
On Oldschoolshaving you will find some hones especially for the razor use

The next thing is, there are many j-nat stones suitable for razor finishing.
Nakayama being the most common one there are however several others I know of producing wickedly sharp and smooth edges.
I myself own a Ohzuku in a perfect size that cost me 70€
and it produces the most keen edge I have ever seen,
even compared to Shapton 16k, vintage thuringian etc.
I would say it is equal to Chromium oxide in 0.5µm

But usually you don´t get to buy such uncommon hones
and your best chances lie in a good but expensive Nakayama.

Let me make one more thing clear:
If you are not able to produce comfortable shaving edges from an synthetic high quality 8k stone
following some pasting or good leathering
you will eventually not benefit from a high grit stone