This movie is an alternate ending to the series, taking place after the events of episode 46. With only six Riders remaining in the Rider War, Shirō Kanzaki feels that time is running short.
This television special is an alternate telling of the Kamen Rider Ryuki story. Shinji Kido's life, working as an employee at ORE Journal, takes a sharp turn after being pulled into the Mirror World by a Mispider. Luckily, he was saved by Kamen Rider Ryuki, Koichi Sakakibara. However, Sakakibara could no longer go on due to the severity of his injuries and passed his Card Deck to Shinji, allowing him to become the next Ryuki and defeat the monster.
Takeshi Hongo is a promising young man with a passion for motorcycle racing. However, his dreams are suddenly ruined when he gets kidnapped by Shocker, the evil secret organization planning to dominate the world. After being remodeled into a cyborg, Takeshi escapes and swears to protect the world from the inhuman monsters.
"Mirror World" exists symmetrically beyond an invisible mirror in space, and an exact copy of our human world, where only monsters can dwell. Evil monsters frequently cross the mirror and attack our world. Only Kamen Riders who make a contract with a specific monster and obtain special power from it, can enter "Mirror World" and fight against evil monsters with the help of an "Advent Card."
Shinji Kido, a journalist, contracts with a dragon and becomes Kamen Rider Ryuki. He fights a fierce battle with evil monsters. Many Kamen Riders appear one after another and fight to satisfy their own aims. However, only one Kamen Rider can outlive others. Thus, it is their fate to keep fighting to the last man.