10 years ago when the Pandora Box was discovered on Mars and brought to Earth, it's activated and creates a Skywall which divides Japan into Touto, Seito, and Hokuto resulting into untold chaos. Along with creating a complex power dynamic between the three regions, the event brings waves of monsters called Smash down on the country, who terrorize and attack the citizens. Sento Kiryu, an amnesiac taken in by a mysterious cafe owner named Soichi Isurugi who provides him with a belt called the Build Driver that allows him to turn into Kamen Rider Build, which he uses to fight the Smash on his own.

Atsuhiro Inukaias Sento Kiryu / Kamen Rider Build
Eiji Akasoas Ryuga Banjo / Kamen Rider Cross-Z
Kensei Mikamias Gentoku Himuro / Night Rogue / Kamen Rider Rogue
Kaho Takadaas Misora Isurugi
Kouhei Takedaas Kazumi Sawatari / Kamen Rider Grease
Tetsuo Kanaoas Evolto / Blood Stalk / Kamen Rider Evol (voice)
Yasuyuki Maekawaas Soichi Isurugi / Blood Stalk / Kamen Rider Evol
Yuki Ochias Nariaki Utsumi / Night Rogue / Hell Bro's / Kamen Rider MadRogue
Yukari Takias Sawa Takigawa
Katsuya Kobayashias Build Driver / Nebulasteam Gun / Genius Fullbottle (voice)
Shogo Muto