Mikiko Lockwood in an article on The Hosta Library titled, A Little About Japanese Hosta Terms defines the term iwa as rock, Iwa Gibōshi or H. longipes.

This cultivar was included in The Genus Hosta with no additional information.

By the name, it is a sport of the species, H. gracillima. This would make it a small size hosta with lanceolate and shiny green leaves (and, perhaps some type of variegation but we do not know). The plant would also bear purple, funnel shaped flowers with purple anthers in September followed by viable seeds.