"Shirofukurin Ko Mame Gibōshi, the "white-margined dwarf hosta."  It is a small size sport of H. gracillima with medium green foliage that has a white marginal variegation. The leaves are lanceolate, flat and 2 inches long by 0.5 inches wide.

Mikiko Lockwood in an article on The Hosta Library titled, A Little About Japanese Hosta Terms defines the term shirofukurin or shiro fukurin as white-edge(d) or white-margin(ed).