When Earth is tearing itself apart by means of crime, pollution and war, aliens choose the time to invade, taking advantage of the lowering of everyone's guard. The Japanese government establishes an elite police organization known as Blue SWAT to combat the aliens, known as the Space Mafia. The aliens attack by possessing humans to obtain their goals. When an alien possesses the chief of the Blue SWAT unit to infiltrate the organization, it manages to completely demolish their building of operations and murder all but three SWAT members; Shou, Sara and Sig.

Blue SWAT

The evil organization Shocker alters history by sending their newest creation, Kamen Rider 3, to defeat Kamen Riders 1 and 2 back in 1973. In the alternate present, Shocker is more powerful than ever, and most of the Kamen Riders are now either imprisoned or brainwashed to work for them. One such brainwashed Rider is Shinnosuke Tomari who thanks to his partner Kiriko Shijima, remembers the truth and joins forces with the remaining Kamen Riders who are still at large to make a stand against Shocker and put history back on its proper course.