Its all Unkh's fault in Let's Go Kamen Riders Movie!

Minor spoiler alert and more images on the upcoming Den-O movie, All Rider: Let’s Go Kamen Rider.

Intro: Kamen Rider OOO starts with fighting with the Mole Imagin thinking that they are Greeds.

This Imagin enters a kid and disappears. Den-liner appears and Kotaro flies back to Nov 11, 1971 - the time when the first Kamen Rider was introduced. Without noticing it, Eiji and Unkh rides the Denliner.

 

Suddenly both were caught by the Imagins aboard. Momotaros advices the two about Denliner and gives a warning not to leave but acting his true nature Unkh jumps of the train (or flies) in hopes to collect all the Medals on the time before the Greeeds were resurrected. Which as scientists say would have a dramatic rift in time. Both out OOO heroes arrives in 2011 to see that Cous Cousier is now called “Snack Amigo”. 

During 1971, Shocker discovered the Core Medal and utilizes it to control Japan and succeeded, by today Shocker already owns the world.

Because of the Core Medal stuck in 1971 Ichigo and Nigo didn't won against the Shocker and fell under the evil group. Both became Shocker's best agents and pegged as “Strongest and Most Evil Cyborg Monsters” together with Black Shogun (Seizo Fukumoto)and Shocker Greeed.

More trouble in 1979 when Shocker created the Shocker Greed using the OOO Medal. It’s mainly based of eagles, but there’s a snake sticking out of his right shoulder. In order to repair time, Kotaro and Eiji travel back to 1971 once more. When they arrive in 1971, they meet Nokko, a member of the Rider Squad.

Also in this movie General Shadow, Kamen Rider Stronger's arch nemesis, returns as well.