In another departure from Kamen Rider norms there is no group of super villians, just a gang of international criminals known as "The Syndicate" (Sigh). Another experiment, financed by the mobsters, resulted in the creation of an android. That android is sent to kill Shin when it becomes clear that Shin will not cooperate with "The Syndicate". The only other monster in this movie is another grasshopper-man, like Shin.
The CIA is also after Shin because they consider him a dangerous weapon. It is the CIA which classifies Shin as "Masked Rider", for no good reason, since he is not masked and doesn't ride a motorcycle.