Trichosanthes kirilowii var. japonica or Karasu-uri 烏瓜 literally the gourd for the crows. Snake gourd is the English common name.
玉章 たまずさ Tamazusa is another name of this plant.
It is easy to spot this vine in the Japanese satoyama countryside during walks.
More facts and links about this plant here.
NATURE IN JAPAN 