I don't think it's Japanese. The hilt style is wrong and the
blade style is wrong. Don't know what it is, but pretty sure
not Japanese. See my Japanese sword site and go to the
various military swords pages for examples of nearly all types
of Japanese military swords.
http://home.earthlink.net/~steinrl/nihonto.htm
or
http://www.geocities.com/alchemyst/nihonto.htm
Rich S