The Japanese Virtua Gun is just the same as the Blue Western one bar the cool Sega Saturn logo on it and the fact that it's black like a gun should be.  The one I have come in a rare'ish special set that included Virtua Cop, Virtua Cop 2 and a Sample disc of House Of The Dead.  Click the images above to see the full size box scans.
The picture above makes the gun look gray when in fact it's black as shown on the picture below.  That Saturn logo looks cool.  No idea why it wasn't included on the western guns.