Season 1

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.

As Kamen Rider Ouja is about to strike a helpless Shinji, Kamen Rider Knight appears and blocks the attack. Ouja then joins the fight with Kamen Rider Gai and Kamen Rider Scissors, while Knight tells Shinji to run. However, the two are stopped by Kamen Rider Raia, who has already betrayed Shinji in the previous episode. Kimura flees from the chaotic battle. Kamen Rider Zolda uses his Final Vent, causing an enormous explosion, forcing the combatants to retreat.

After witnessing a sudden death at the hands of Dark Shinji, Kimura and Ren are shocked. Ryuga then attacks Kimura, wanting Kimura to die for him, saying that if he wins the Rider War, he can escape to the real world and exist as a real being.