In the fictional land of Huaxia's Nine Regions, outward prosperity conceals surging undercurrents. Ancient legacies and modern technology intertwine, while the nine core cities are quietly infiltrated by the mysterious organization Shadow Alliance and its terrifying monster groups from various Kamen Rider series, including the Gurongi, Orphnochs, and Bugsters. Through reverse engineering, the native organization known as the Source Energy Research Institute equips local warriors with Rider Systems originating from outer space, the future, or magic. The main Heisei and Reiwa Riders, including Kuuga, Faiz, Den-O, Build, Saber, and Geats, all make their appearances, battling the Shadow Alliance in their respective cities to protect their homes.
Lin An, a young man from Liulijing, had no connection to the supernatural until a mysterious fragment of a dark ring unexpectedly awakened within him the dangerous power of the cosmic demon Juggler during a Gurongi death game. Wielding the Snake Heart Sword, forged from dark purple energy, and suffering the backlash of an unstable transformation into a demon, Lin An is dragged into a war beyond anything he could have imagined. Kuuga views him with suspicion, the Source Energy Research Institute hunts him, and the lens of the mysterious traveler Decade is fixed on him.
Refusing to be consumed by power or reduced to a research subject, Lin An relies on his keen mind and instinctive understanding of technology to walk a thorny path: **analyze Juggler's dark power, use technology as a bridge, and master the abyss!** He handles the remains of Riders, studies energy data, and builds his own guiding devices, struggling to survive on the brink of losing control. When the Shadow Alliance's ultimate conspiracy threatens all nine regions and all Riders are forced to unite, Lin An finally completes his own transformation: fusing cutting-edge technology with Juggler's true essence
