Vic,  Careful there, that unit is most likely designed for 110-120
volts AC, and I don't know what they have in Japan -- it could be
220 volts.  Find out what's coming out of the wall before you make
connections.  I doubt that electrical arc displays will be looked on
favorably by the management.  And, to be perfectly clear, black is
hot and white is neutral, green is ground [only in USA. -- Robbie].
If you are not grounding the unit, do check to see which blade of
the plug should be neutral, just for safety's sake.

David Dewey