In the near future, the world is ruled by the Smart Brain Corporation, with 90% of the population being Orphnoch, and the once prominent human race is nearing extinction. Takumi Inui, Kamen Rider Faiz, was once regarded as mankind’s savior until, in an attack by Smart Brain troops, he was presumed dead. Since then, human rebel groups have staged attacks on Smart Brain’s complex in an attempt to steal the top-secret Emperor Belts, with no success. Kiba Yuji, Naoya Kaidō and Yuka Osada attempt to ease tensions between both races but their peace meeting is interrupted by Smart Brain troops and their newest warrior, Kamen Rider Psyga. Takumi, believing himself a young cobbler named Takeshi, regains his memory and becomes Kamen Rider Faiz again to settle things with Smart Brain once and for all.
The story begins with a regular day with Takumi, Mari and Keitaro, which suddenly turns into a musical number thanks to a mysterious new boom box created by Smart Brain. As it turns out, Yuji, Yuka and Naoya have the same boom box and are greeted by a rapping Smart Lady who reveals that it's part of a new plan by Smart Brain to invoke people into singing all over Japan. The reason: To get the three Rider Belts back!
Released to commemorate Kamen Rider 555's 20th anniversary, the film takes place after the ending of the TV series. Masato Kusaka and Mari Sonoda are fighting a new iteration of Smart Brain led by Kitazaki, who begins an operation to exterminate all Orphnochs, with Takumi Inui seemingly working with them for unknown reasons since his disappearance.
