Takatora Kureshima (Kamen Rider Zangetsu) visits a former Yggdrasill Corporation experimental project site located in the poverty and conflict stricken Republic of Torukia. He is visiting the site for the first time in 8 years, and is suddenly attacked! Suprised he stumble and falls into a giant hole which leads into an underground city. This underground city is the most dangerous place in the republic, in which many young men are killed defending themselves while trying to survive. These men use Lock Seeds and Drivers to transform into Armored Riders. Due to the fall Takatora has lost his memory. He is helped by the leader of Team Orange Ride. Unbeknownst to them, there are cameras hidden all around the underground city. The ones behind the cameras are responsible for the conflicts in the city. One man in particular is seeking revenge on Takatora for a specific reason...
久保田悠来
as Takatora Kureshima / Kamen Rider Zangetsu
Keigo Hagiya
as Aym / Kamen Rider Proto Gaim
後藤大
as Paimon
Keito Takahashi
as Gusion
Atsuki Masuko
as Glasya / Kamen Rider Proto Baron
Kyohei Chida
as Berith
Rui Tabuchi
as Ose
Ketsuya Uno
as Foras / Kamen Rider Proto Gridon
Shota Onuma
as Yukimura Belial Granstein / Kamen Rider Proto Bravo
Haruki Kiyama
as Masahito Shizumiya / Kamen Rider Zangetsu
Motohisa Harashima
as Kagemasa Shizumiya / Kamen Rider Proto Ryugen
大高洋夫
as Kagiomi Shizumiya
