An article by W. George Schmid in The Hosta Journal  (1996 Vol. 27 No. 2) states that This is a duplicate, incorrect or outdated name for Hosta longissima longifolia 'Nakafu Nagaba Mizu'.

Mikiko Lockwood in an article on The Hosta Library titled, A Little About Japanese Hosta Terms defines the term nakafu as medio-variegated, the term nagaba as narrow long leaf(ed). and the term mizu as water or 'Mizu Gibōshi' which is the Japanese name for the species H. longissima.

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'.