Saigetsu, Mimei, and Tasogare of a mysterious organization appear before Houtaro and the others. The three, who say they are looking for a super weapon in this world, call in the Kasshine army to attack the people.

We will stop them! In front of Houtaro and the others, who are furious, Saigetsu and the others transform into Kamen Riders such as Dark Kiva! Houtaro, Rinne, and Supana also transform into Riders and stand up to them...!