Natsukawa accidentally travels to a utopian futuristic world, however, hidden secrets lie beneath the seemingly calm waters. At the same time, the power of the world of Kamen Rider quietly appeared, and since then, the story journey of Kamen Rider belonging to Natsukawa has officially begun! ……………… However, looking at the giant standing on the earth in front of him, Xia Chuan felt that something was wrong in his heart, how could there be Ultraman in the world of Kamen Rider?