Wow... I'm not quite sure what to say...
Browsed through wikipedia -- apparantly this is from the 1992 DTV movie Shin: Kamen Rider Prologue
http://en.wikipedia.org/wiki/Shin:_Kamen_Rider_Prologue
It seems like it could be interesting in the same way DC's Elseworlds stories were interesting. IE as a markely different yet self contained take on the "hero" (or in Kamen Rider's case, the franchise).
