When a novelist discovers a mysterious book, he is transported to a world where he must join forces with the legendary Kamen Rider Saber and Kamen Rider Ghost to save humanity from an evil clone army.

Serving as a sequel to Kamen Rider Saber × Ghost, Rintaro joins forces with both Makoto Fukami and Kanon Fukami to take down the remnants of Danton's evil forces.