This non-registered cultivar is a sport of H. longissima longifolia from Japan. It forms a small size plant with green foliage that has a yellow medial (center) variegation. Pale lavender flowers with 4 or 5 blossoms per scape bloom in September.

H. 'Kinakafu Nagaba Mizu' has been known by many, many different names in its native Japan. According to The Hostapedia by Mark Zilis (2009), "It may be the same as the plant sold as 'Asahi Star'...Adding to the confusion is the name 'Kinakafu Hosaba Mizu', which some plants might be legitimately labeled since 'Nagaba Mizu' and 'Hosoba Mizu' are both accepted names for H. longissima longifolia."

Mikiko Lockwood in an article on The Hosta Library titled, A Little About Japanese Hosta Terms defines the term hosoba as narrow leaf, the term mizu as water, 'Mizu Gibōshi' or H. longissima, the term nagaba as narrow long leaf(ed). and the term kinakafu or ki nakifu as yellow-center(ed).