Yuumi Shida

Hana Ichii attends a school that she admired since she was a child. One day, she wakes up and finds herself locked in a cage with her classmates. They are forced to take part in a survival game using their cellphones.

The Underground Empire Badan makes its move, intending to invert the world. Kouta and Mai are pulled through one of these inversions where the discover a boy named Shu, who also holds the power to invert the world. As the Riders fight to protect Shu, Fifteen appears again, seeking Shu. As Kouta flees, past Riders gather and fight one another, split between the Showa and Heisei era Riders. But, the truth of Badan is not as it seems…