After the events of the TV series, the 18 year old Yoko Godai has abandoned her special agent Saki Asamiya name to return to her normal life, and is now studying for college entrance exams. However, she accidentally bumps into a young man named Kazuo Hagiwara trying to escape from a group of hitmen, and learns that he comes from Sanko Academy, a private school located in a remote island known as Hell's Castle. The school is ruled by a former revolutionary thought to be dead named Hattori who is trying to brainwash students into terrorists to help him stage a fascist coup d'etat in Japan.

A young Kamen Rider fan is granted his wish of seeing Riders in person, initiating the ultimate Japanese superhero crossover meta film. The third and final installment of the Heisei Generations series finds Kamen Rider Zi-O and Kamen Rider Build joining forces with all of the other Heisei Generation Riders to reverse the damages of an evil Time Jacker named Tid, and save their legacy. Are Kamen Riders real? Will you believe?

The Quartzers, calling themselves the Wardens of Time, appear after Sougo Tokiwa has collected all of the Heisei Era Ride Watches. A grand conspiracy behind the birth of the King of Time becomes ever clearer...

After the end of the civil war that tore apart Japan, the new governors of Touto, Hokuto and Seito work together to reunify the country. However, they are actually members of an extraterrestrial race called the "Blood Tribe" (the same species as Evolto), who assumed their government positions as part of a plan to destroy Earth as they have done to Mars and other planets before. Considering Sento Kiryū (Kamen Rider Build) a major threat to their plans, the Blood Tribe manipulates his friends and other civilians into attacking him. With even his close ally Ryūga Banjō (Kamen Rider Cross-Z) now against him, Sento must fight to survive and stop the Blood Tribe's plan from succeeding.