The Destroyer of Worlds

Destroyer of Worlds (世界の破壊者) is the thirty-first and final episode of Kamen Rider Decade.

On October 4, 2009, TV Asahi began a re-broadcast of the series from beginning to end at 6:30 am timeslot. When episodes 30 and 31 were rebroadcast on May 2 and 9, 2010, respectively, they were recut with some scenes extended and others cut, labeled as "Special Edition" (特別編) versions.

Synopsis
to be added

Original version
After fighting off the Riders, Super Apollo Geist takes Natsumi to be his new bride as he flees. Kazuma Kenzaki appears, saying that Tsukasa's existence is the real cause of the worlds blending before confronting him as Kamen Rider Blade in King Form in order to force him to leave the world at once with Asumu keeping Yusuke and Wataru from interfering as Decade is easily defeated. After returning to the Hikari Studio, Tsukasa is recuperating while learning that all of his photos are starting to vanish as a result of the worlds' fusion; Eijiro gives him hope with a photo of Natsumi and tells him not to give up. Following Kiva-la, Tsukasa is attacked by Wataru and Asumu, whom Kenzaki recruited so they can save their worlds, after he refuses to leave. Kuuga gets Tsukasa to run off so he can save Natsumi while he holds Kiva and Hibiki off, though briefly torn by his loyalties. Meanwhile, Super Apollo Geist resurrects the Beetle Fangire, Paradoxa Undead, Tiger Orphnoch, Taurus Ballista, Alligator Imagin, and the Phylloxera Worm. The next day, Tsukasa finds Super Apollo Geist's base as he meets Daiki who warns about the trap arranged for him. After promising the world to Daiki if he dies, Tsukasa arrives to stop Guy as he is about to consume Natsumi's life energy, fighting both Super Apollo Geist and the monsters with aid from Kuuga and Diend. With Kiva and Hibiki joining the fight, the Riders take out the monsters. After Yusuke gets injured protecting him, Decade uses Diend's Final Attack Ride card to kill Super Apollo Geist. With the battle over, Natsumi soon recognizes that she is in the exact place where her dream takes place as Kiva and Hibiki fade away with the Nine Worlds destroyed, with only Yusuke surviving. Tsukasa is suddenly transported to the dimension where he had spoken with Wataru Kurenai, who becomes Kamen Rider Kiva after telling Tsukasa that he failed. Soon, Tsukasa finds himself back in the World of the Rider War, confronted by the eight of the nine other Heisei Kamen Riders. Kiva-la then bites Yusuke, turning him into a black-eyed Kamen Rider Kuuga Ultimate Form. With Narutaki overseeing it, the Rider War commences with Diend suddenly firing the Diendriver at Decade at point blank range.

Special version
After fighting off the Riders, Super Apollo Geist takes Natsumi to be his new bride as he flees. Kazuma Kenzaki appears, saying that Tsukasa's existence is the real cause of the worlds blending before confronting him as Kamen Rider Blade in King Form in order to force him to leave the world at once with Asumu keeping Yusuke and Wataru from interfering as Decade is easily defeated. After returning to the Hikari Studio, Tsukasa is recuperating while learning that all of his photos are starting to vanish as a result of the worlds' fusion; Eijiro gives him hope with a photo of Natsumi and tells him not to give up. Following Kiva-la, Tsukasa is attacked by Wataru and Asumu, whom Kenzaki recruited so they can save their worlds, after he refuses to leave. Kuuga gets Tsukasa to run off so he can save Natsumi while he holds Kiva and Hibiki off, though briefly torn by his loyalties. Meanwhile, Super Apollo Geist resurrects the Beetle Fangire, Paradoxa Undead, Tiger Orphnoch, Taurus Ballista, Alligator Imagin, and the Phylloxera Worm. The next day, Tsukasa finds Super Apollo Geist's base as he meets Daiki who warns about the trap arranged for him. After promising the world to Daiki if he dies, Tsukasa arrives to stop Guy as he is about to consume Natsumi's life energy, fighting both Super Apollo Geist and the monsters with aid from Kuuga and Diend. With Kiva and Hibiki joining the fight, the Riders take out the monsters. After Yusuke gets injured protecting him, Decade uses Diend's Final Attack Ride card to kill Super Apollo Geist. With the battle over, Natsumi soon recognizes that she is in the exact place where her dream takes place. Kiva and Hibiki fade away and the light of the world changes taking a slightly darker tone. Tsukasa is suddenly transported to the dimension where he had spoken with Wataru Kurenai, who becomes Kamen Rider Kiva after telling Tsukasa that he failed. Soon, Tsukasa finds himself back in the World of the Rider War, confronted by eight other Heisei Kamen Riders, soon followed by an Ultimate Kuuga with Black Eyes. With Narutaki overseeing it, the Rider War commences as a huge Rider army joins the brawl. After the chaos, Decade emerges victorious, with many Riders dead around him, while Natsumi wonders about the meaning of their journey and Decade's battle.

Cast
to be added

Kamen Rides

 * Decade - Complete Form
 * Decade Complete Form - None
 * Diend - None

Trivia

 * As part of Super Hero Time, this episode aired alongside Samurai Sentai Shinkenger episode 27, Switched Lives.
 * In the version of Kamen Rider Decade episode 31 shown in reruns, an unidentified Ultimate Kuuga, with black eyes, appears as one of Wataru Kurenai's companions, who antagonize Decade after he failed in his mission of saving the worlds. When more Riders appear and the Rider War starts, Kuuga seemingly reverts to Mighty Form and boards the TryChaser 2000, although he's knocked out during the conflict.
 * In the original version of the episode, the Ultimate Kuuga in the final battle was a brainwashed Yusuke Onodera, but all references to his identity are removed in the rerun version, which just makes him appear as another member of Wataru's group. TV Asahi site also lists this Kuuga as a separate character.
 * The Rider War stopped in a cliffhanger. Continuity started during the W and Decade Movie War 2010.