An article by W. George Schmid in The Hosta Journal  (1996 Vol. 27 No. 2) states that this is an "old" incorrect name for Hosta kiyosumiensis 'Nakafu Kiyosumi'.

Mikiko Lockwood in an article on The Hosta Library titled, A Little About Japanese Hosta Terms defines the term nakafu as medio-variegated.

There are at least 3 hostas with this Japanese name but they are each of a different species as follows: H. cathayana 'Nakafu', H. kiyosumiensis 'Nakafu' and H. longissima var. longifolia 'Nakafu'.