Kadoya Tsukasa

A guy who travels dimensions and appears as a normal person in them. Kamen Rider lore is hard.

The Destroyer of Worlds
An orphan, he and his sister Sayo were in the care of the family's butler, Nobuhiko Tsukikage. Sayo was scared of the outside world, which manifested her abilities to open "Dimensional Walls" to other worlds, which Tsukasa used to travel, annoying his sister as she was all alone without him. At some point his constant use of the walls had him gain the same ability as his sister. His constant travels across Kamen Rider worlds lead the villains of respective worlds to notice it and form the Dai-Shocker multiversal evil organisation, appointing Tsukasa as Great Leader of Dai-Shocker, and making the Decadriver and Ride Booker for him. However, one year later his abuse of Dimensional Walls slowly made him lose his memory until he became totally amnesiac when he arrived in the World of Natsumi.

He meets Natsumi Hikari, a girl who had been seeing him in her dreams, before accidentally opening a Dimensional Wall, and she is sent to a pocked dimension and attacked by several Kaijin. In his pocket dimension, he meets Wataru Kurenai, who addressing him as "Decade", tells him his world is ending and needs help. Natsumi finds the Decadriver that he had lost due to his amnesia, and after he meets with her, gives it to him, and proceeds to transform into Kamen Rider: Decade. After helping in Wataru's world, he and Natsumi return to their own world to find it being destroyed by Kaijin. Wataru arrives and uses all his power to put the world into stasis, and assigns Tsukasa to the task of travelling all of the "Nine Worlds" and help each's Kamen Riders.

As a police officer, Tsukasa meets the world's Rider, Yusuke Onodera who battles the Gurongi and learns that that someone is disseminating rumors across the Worlds about him as the World Destroyer. After reconciling with Yusuke, the two stop the Gurongi from taking over the world. As a violinist, Tsukasa encounters younger Wataru, helping the boy realize his role as King of the Fangire Race to maintain the peaceful coexistence of the human and Fangire races while defeating the Beetle Fangire: Wataru's father and the former King. Tsukasa defends the framed Natsumi in a murder case and solves it with the aid of Shinji Tatsumi. The true villain, Kamata is revealed to have been an Undead all along and is taken by Narutaki, a person protected by an aura who travels the world telling of Tsukasa coming to destroy them, to the World of Blade after his defeat. As chief waiter under the BOARD Corporation, Tsukasa works with Kazuma Kendate to uncover the conspiracy between Kamata and BOARD's CEO, Kamen Rider Chalice, to take over the world through the Joker card. As a student of the Smart Brain High School, Tsukasa crosses paths with a man he saw at the World of Blade who knows him, Daiki Kaito. Though Kaito warns him to stay out of his affairs, Tsukasa finds Faiz after confronting the Lucky Clover group, learning that he is Takumi Ogami. As a postman, he reads a discarded letter meant for Shouichi Ashikawa, making it his goal to protect Ashikawa from the Unknown for the sake of Toko Yashiro, the writer of the letter. With Yusuke Onodera's help, Tsukasa succeeds in having Shouichi achieve the necessary state of mind needed to complete his evolution to Agito before reuniting him with Yashiro. Tsukasa becomes Den-O under the possession of an Imagin(originally beings from the distant future who lost their physical forms due to an event in the past erasing their own time, becoming dependent on the memories of others in order to survive), before forcing him into Yusuke Odonera's body. Here, he learns that some unknown force is changing the past as he is fought by the other Taros possessing Natsumi's body who believe Decade to be the source. Learning the Imagin possessing Yusuke is named Momotaros, Tsukasa finds him and helps him regain his physical form as they defeat the Alligator Imagin. Believing their adventures with Den-O to be over, only to learn the identity of the true culprits for Den-O World's time distortions, they prepare to travel to the World of Kabuto until the Swan Imagin Sieg comes into the Hikari Studio. With Sieg's help, Tsukasa and company travel with the DenLiner crew back in time to fight the Oni Rider Brothers, Mimihiko and Kuchihiko, before returning to the present time in the World of Kabuto. In a ZECTrooper role, after witnessing TheBee and Gattack's fight against one of the alien lifeforms Worms, Tsukasa brings Arata to the Photo Studio where he finds a Salis Worm that had mimicked him. After the impostor is exposed, the Worm is killed by Kabuto when it attempted to kill a girl named Mayu whose brother was believed to have been killed by Kabuto. Although it seemed that TheBee's user, Sou Otogiri, is her brother, Tsukasa felt something was not right. After learning that Mayu herself is a Worm, both his meeting with her grandma and learning the full nature of the Kabuto Capture Plan allow him to get the full story. Arriving to Mayu's aid, Tsukasa helps Kabuto, Mayu's real brother Souji, in defeating Otogiri in his true identity, the Phylloxera Worm. Tsukasa meets and encounters an Oni in training named Asumu. From there, believed to be the Great Master of Ongekidō (音撃道 Ongekidō) style, Tsukasa meets the three masters of the Ongekidō Styles before being pulled into a ploy by Daiki Kaito to rob the two Oni masters Ibuki and Zanki, worsening when they are attacked by the Makamou Gyuki until Akira and Todoroki drive the beast off. Supporting their intent to end the rivalry among their schools, Tsukasa convinces Ibuki and Zanki to pass the torch. With the journey over, Tsukasa and the others of the Hikari Studio return to what appears to be Natsumi's world to find it back to normal as if it was not plagued by the monsters. Despite being in a perfect world that he has earned, according to Otoya Kurenai, it is revealed that it is only a parallel version of their own world where the monsters have taken over and killed all but a few humans.
 * -|World of Kuuga=
 * -|World of Kiva=
 * -|World of Ryuki=
 * -|World of Blade=
 * -|World of Faiz=
 * -|World of Agito=
 * -|World of Den-O=
 * -|World of Kabuto=
 * -|World of Hibiki=

Season 3
Now his travels across realities have lead him to yet another new world, The World of The Final Rumble, in this new world he appears a wrestler in TFR 's ring. Intrigued, he wants to learn more about this world, find the Rider(s) that reside in it, try to do good, and ultimately, decide if it's bears danger to other universes and destroy it if it does so.