When the evil organizations have been vanquished by all of the Kamen Riders, the peace has been restored where they live in a happy life once again. But one day, a mysterious voice appeared in their sense of hearing by telling them to follow its lead, so they went somewhere in a hidden place and found a bright shining light. Then, they get closer to it, causing a light become more brighter by getting them transported to another world where humans, monsters, and other species that exists and lived together. However, the Tokyo have been taken over and became corrupted with their wrongful deeds by the notorious organization called NOMAD, led by Edwin Black. But when the Showa Riders geared themselves up, they're going to fight against NOMAD, while also protecting the people's lives from getting into a horrible situation as possible.