1x1 - Rider Time: Kamen Rider Ryuki

A mysterious woman brings 13 people into the Mirror World to restart the Rider War. Among them are Shinji Kido, Ren Akiyama, Jun Shibaura, Goro Yura, Miyuki Tezuka and Takeshi Asakura. These 13 people (aside from Asakura) have no memories about their past. The woman tells them to fight each other, and the winner must be found on the 7th day. The winner will be released from the Mirror World with restored memories.