The Summer Movie for Kamen Rider Build. Set after the events of the Japanese Civil War, the newly appointed governors of Seito, Hokuto and Touto now support each other in their mission to reunify Japan, however they are secretly members of Evolto's home clan known as the Blood Tribe, who each have assumed government positions in order to take over the entire world. Being certain that Sento Kiryu/Kamen Rider Build is a major threat to their plans, they proceed with their Build Annihilation Plan to manipulate Sento's friends and other civilians against him. With Ryuga Banjo now against him, Sento must find a way to fight and survive as he hunts for the truth to stop the Blood Tribe in succeeding with their ultimate plan.