Looks like an Alien, but there were several knock-offs also. Here is the 1990 Nishiki Alien ACX lit, and you can see that the rear triangle is completely different.
definitely an alien sp. the earlier alien al had the strengthened rear e-stay like the acx in repack rider's post. but then they dropped it for the sp. think they did the sp from about late '91 to about '93 (but don't quote me on that :? )