The superstones are on the softer end of the spectrum. You will without a doubt need a stone fixer to lap with.
In my limited experience I spend my time on a dull edge:
90% on 1k
9% on 2-5k aoto
1% on 8k kitayama
So to me a 12k seems like it's not the most important stone to have.
Is this because you generally like to hone as an enthusiast? :hmmm:
Or do you believe that most blades that need a refreshing (when a strop don't cut it) need to start from a grit level lower than what the nani/chinese 12k offer?