Airi Yoshida

After the end of the civil war that tore apart Japan, the new governors of Touto, Hokuto and Seito work together to reunify the country. However, they are actually members of an extraterrestrial race called the "Blood Tribe" (the same species as Evolto), who assumed their government positions as part of a plan to destroy Earth as they have done to Mars and other planets before. Considering Sento Kiryū (Kamen Rider Build) a major threat to their plans, the Blood Tribe manipulates his friends and other civilians into attacking him. With even his close ally Ryūga Banjō (Kamen Rider Cross-Z) now against him, Sento must fight to survive and stop the Blood Tribe's plan from succeeding.

Less than a year after Geist activated the Death Force, which decimated most of Jerra's population, he has kept himself busy by dismantling the Death Force machines one by one. Most of the remaining human population have fled to a remote haven run by a warlord named Krauser. Krauser is another MDS unit, MD-01, who has a technology that hides his mobile fortress from the Death Force.