This is a green hosta with white streaks in the foliage. It
is a medium size sport of the species,
Hosta kiyosumeinsis, from
foliage is slightly wavy and faintly corrugated. Pale lavender
flowers bloom from mid-July into August.
Mikiko Lockwood in an article on The Hosta Library titled,
A Little About Japanese Hosta Terms defines the term
-gawa or -kawa as river.