The Collaborative International Dictionary of English v.0.48:

Japan current \Japan current\
   A branch of the equatorial current of the Pacific, washing
   the eastern coast of Formosa and thence flowing northeastward
   past Japan and merging into the easterly drift of the North
   Pacific; -- called also Kuro-Siwo, or Black Stream, in
   allusion to the deep blue of its water. It is similar in may
   ways to the Gulf Stream.
   [Webster 1913 Suppl.]