Has the world suddenly split into four? Keiwa Sakurai, Neon Kurama, Michinaga Azuma, and Tsumuri are flung into different worlds. And for some reason, a different Ace exists in each of the four worlds. The cause seems to be from the "World Doomsday Game" started by the staff from the future. In light of this crisis, the mysterious Cross Geats appears. Just what will happen to Ace and his friends?

In a world where people awaken to supernatural powers, one ordinary police officer Makoto Hikawa stands against this chaos.

Niramu, who has just been appointed as a DGP producer, goes to the Sengoku period in Japan for his first job. There, he learns about the "realism" of this era from the navigator, Miiru, and savors the valuable experience. Meanwhile, Nemeru, a veteran producer who has been active in DGP since its inception, makes a suspicious move... Realism and fiction - what is necessary for true entertainment?

The "Desire Grand Prix" is a game to protect the peace of the city from the threat of the mysterious enemy "Jyamato", whose origin and purpose are unknown. Each participant transforms into a Kamen Rider and competes to win the game by defeating enemies and saving people. The winner of the Desire Grand Prix will be rewarded with "the right to bring an ideal world to life" as a prize. In other words, only the true heroes who win the competition will be able to realize the world they have wished for.

Shouichi encounters a teenage girl called Sayaka, who ran away from a military facility because of an attack by the Ant Lords. Sayaka has a supernatural ability to foresee the future. Risa Fukami, of the military group GA, wants to use that power to enhance the newly-made G4 System, which was based upon designs stolen from Ozawa. Now, Agito and Gills must fight to stop the Ant Lords' attack, as G3 and G4 settle their score.

Leading an expedition in Germany, Kougami unseals the resting place of one of the alchemists that created the Core Medals in an effort to retrieve a set of lost Medals. However, upon the seal being undone, millions of Cell Medals erupt into a tower while creating a magical barrier that causes parts of Japan to flip over. As the alchemist reveals her plans to become a new OOO, Eiji and his friends are thrown into the past and must find their way back home and stop the alchemist before she destroys the world!

Under the impression that they saved the World of Den-O, Tsukasa Kadoya (Kamen Rider Decade) and company begin their journey to the World of Kabuto when they are halted by Sieg who presents them a manuscript that detailed the legendary Oni Conquest with Momotaros' image on it. As this occurred, the Tarōs mysteriously vanish from the DenLiner as they are about to help Kotaro Nogami (Kamen Rider New Den‑O) out with the true threat to their world.

The Quartzers, calling themselves the Wardens of Time, appear after Sougo Tokiwa has collected all of the Heisei Era Ride Watches. A grand conspiracy behind the birth of the King of Time becomes ever clearer...

Confronting a mysterious enemy, the Pteranodon Yummy, Kamen Rider W receives aid from Ryu, who has infuriated Akiko by being too busy to attend her wedding! Akiko demands to know why he even became a Kamen Rider in the first place and the Pteranodon Yummy as it uses the Memory Memory on her to give her the answer to her question. Meanwhile, at the Kougami Foundation, Kousei Kougami talks of the most avaricious man in Japan, Oda Nobunaga, whose final resting place was found. With Doctor Maki overseeing the process, Kougami commissions the creation of a Cell Medal homunculus based on Nobunaga himself. Later, Kamen Rider Core begins to destroy the area as Kamen Riders OOO and W team up to fight the enemy. However, Kamen Rider Core proves too powerful and the two go underground to destroy the Gaia Memory’s source of power to even the odds.

Movie War Mega Max featured the first seven Kamen Riders (Kamen Rider 1, 2, V3, Riderman, X, Amazon, and Stronger) to commemorate the franchise's 40th anniversary. Trailers for the film shown during airings of Fourze also showed the return of Kamen Rider Double as well as a new form for Kamen Rider OOO. Unlike previous Movie War films, where they were divided into 3 segments, Movie War Mega Max is divided into 5 parts. Like previous Movie War films the secondary Kamen Rider of Kamen Rider Fourze, Kamen Rider Meteor, made his debut in the film.

When the Imagin and Kohana take a trip to visit Ryotaro and Airi, they are attacked by the legendary Ghost Train, and onboard are two Imagin and the evil Kamen Rider Yuuki, who is none other than Ryotaro! But when all hope seems lost, a blue DenLiner appears, delivering someone claiming to be Kamen Rider New Den-O! Just who is he, and can he help everyone save Ryotaro and save time once again?