Kadoya Tsukasa

The main character of Kamen Rider: Decade, a guy who travels dimensions and appears as a normal person in them. Kamen Rider lore is hard.

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.

Episode 2
Turns Chosen Hunter into a yugioh card after BTFOing him in the ring.

Episode 3
Confronted by Mitake Miyao under suspicion of killing his father. Fights him in the ring and spares Miyao after defeating him. His rider decade form is in fact his persona.

Episode 4
Miyao confronts Kadoya again and questions why Kadoya spared him. Kadoya explains that he believes Miyao is just a naive kid that doesn't know any better.

Kadoya mulls over his own inability to save the world and what he holds dear, but is convinced by Miyao to help his friends go against their destiny and to assist in their efforts to change the world.

Teleports Nagito Komaeda,Makoto Yuki, and Tatsuya Suou to safety when the rumbling grows to its tipping point.

Episode 5
He and his group arrive in the diamond realm and meet Yasuhiro Hagakure who offer them Jah's blessings to get stronger after defeating certain apparitions in the area.

Reveals himself to be an alternate Tatsuya Suou who received assistance from a complex individual to travel to this new world to stop the events of Battler/47's altercation and the rumbling from happening but failed when his memories became muddled during the merging events of Season 3.

In order to receive the last Jah's blessing to get stronger, he fights Tatsuya for the right to have it but is defeated by his other self.

The group then travels to the world of TFR twelve years into the future and catch up the situation of the resistance. They decide to watch various qualifier matches of their aged peers that are fighting over spots on the resistance raid teams.

Episode 10
Realizes that even in this timeline the forces of Law and the Troubleshooters will attack the resistance. Fights Adam Jensen but is defeated, but uses the last moments of his life to unlock the gates trapping the Resistance. Dies in the arms of Suou Tatsuya.