Disclaimer - Code Geass is not owned by me It is owned by Sunrise. Neither is Kamen Rider it is owned by Toei.
On with the show
At the Hikari Studios after the intense battle with Super-shocker the Decade team can finally breath a sigh of relief. "I wonder if our journey is going to continue? Natsume said. Tsukasa replied "Yeah I'm going to keep on traveling after all that journey itself is my world. Kaito responded not just you Tsukasa we'll be going with you that's our world too Kivala then flew in and said " That's right! we're all traveling companions! Right? They all put there hands on the backdrop drop and to there suprise showed the Code Geass World.
This implied that there would be another world to go to and all four Riders knew that a new battle had begun.
In Black's world Minami Kotaro was mourning the loss of his brother Nobuhiko. He had recently defeated him and the Creation King and was on his way to a new life. When a portal was opened the portal suddenly pulled him in and closed in an instant. At the same time the Den-Liner was on it's way thru time and space. Momotaros was sleeping while Urataros talks with Deneb. Kintaros is practing his martial arts while Ryutaros is praticing his dance moves. Everything was going well until a temporal anomaly started affecting the train and everyone in it. The red Imagin said "what the hell is going on here" Urataros look out the window and said " We seem to be caught in a storm sempai" Then the train started moving like a roller coaster everyone started heading to who knows where.
The same thing was happening to every other past and present Kamen Rider was being sucked to this portal some tried to resist it liked Kamen Rider Amazon but failed in the end. It wasn't just the heroes that it was going after as well it was also going after the villans. Narutaki was transported as well as most of the former Dai-Shocker organzation that survived was being transported to this new world. The worlds were merging together and so their paths would cross.
I know this is not my best but it'll get better I promise. Until next time Raxius out.