在神秘事件的调查中， Guerra Yue（佐野岳 饰）深入诡异的海姆森林，目睹了一位年轻男孩遭到巴丹帝国的怪人攻击。正在准备变身铠武之时，出现一个似乎风格高仿武士的男子，大声吼“变身”！随后以假面骑士1号的形象出现，原来他就是传说中的男子本乡猛（藤冈弘 饰）！假面骑士1号 lightning-fast pace eliminated the surrounding monsters. In this peaceful era of Showa and Heisei, the two generations of justice knights met for the first time, but Guerra Yue was puzzled by this legendary masked rider who resembled his father's age.
Meanwhile, Masked Rider Decade (井上正大 饰) actively contacted the 15 Masked Riders of the Heisei era. They also established contact with Guerra Yue. A series of terrifying events were evidently orchestrated by the Barand Empire, with the aim of destroying humanity. The active Heisei Masked Riders encountered Local Hero Tsurugi's Showa Masked Knight Team. However, Local Hero Tsurugi believed that the source of Barand's rampage was linked to the Heisei Masked Riders.
With both sides holding firm to their beliefs and clashing head-on, the war between the Masked Riders finally erupted. As the evil plans of the Barand Empire continued unabated, the joining of the Fangire Killer Squad and the Beast Electrical Team increased the complexity of the battles...
