This non-registered cultivar of unidentified parentage was introduced in Japan by Dr. Shuichi Hirao. It is a small size (9 inches high) plant, but there is some confusion about the color of the foliage. The flowers are lavender colored.

According to The Hostapedia by Mark Zilis (2009), "...I first saw the plant described here in the Soules Garden collection... I noted that it made a small size mound of narrow, wavy, shiny, bright gold foliage that seemed to glow at dusk...Sometime in the mid-1990's, however, another 'Kirishima' started showing up in a few collections. While this plant also makes a small size mound of foliage, the leaf color is a shiny, dark green.."

"...named for a large volcanic mountain range in south-central Kyushu, primarily Kagoshima and Miyazaki prefectures. An intermediate between H. 'Saishu Jima' and H. 'Yakushima Mizu'. The taxon cultivated in Europe may be an interspecific hybrid between H. gracillima and a form of the all-green H. sieboldii growing in southern Japan. A taxon cultivated in North America under the same name is different - very small, with chartreuse to very light green leaves, 3 pairs of veins. This name is used for several different cultivars and is confusing."

Mikiko Lockwood in an article on The Hosta Library titled, A Little About Japanese Hosta Terms defines the term mizu as water, 'Mizu Gibōshi' or H. longissima.