This story takes place during the Dazzling Adagio Arc.

Mackenzie King is an avid Kamen Rider fan, though he had been disillusioned with one of his favorite Kamen Riders, Gou Shijima. With the help of a mysterious merchant, he fulfills his dream of being Kamen Rider Mach. However, he is thrust into a world where multi-colored humans live, with him ending up in an academy that views him less of a human and more of an experiment.

If that wasn't bad enough, his appearance got the attention of Foundation X, who seek to retrieve his Driver, even if it means killing Mack in the process. Mack must try to keep on his toes with both them and the scientist who's looking over him, Twilight Sparkle, in order to stay alive in this Mach Speed side to A Golden Drive Through Equestria.