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?

Baku and Nem become members of the Kaiju Countermeasure Agency. The giant robot, Code Zeroider is humanity's hope in the face of evil monsters! But the monsters are strong, and to save the pilots in dire straits, the Ultra Big Kamen Rider ZEZTZ descends!

警察厅遭到炸毁，执行犯竟指向万津莫（今井龙太郎饰）。国家公安委员会随即向怪事课下达逮捕令，但小鹰贤政（古川雄辉饰）与富士见、成华坚信其清白，一直在暗中追踪真凶。与此同时，国家公安委员长玖门宗马向全国宣告万津莫及其所属的情报机关CODE为国民公敌，大众的仇恨被不断激化。在一片混乱中，小鹰终于锁定了幕后黑手——能够驱使白日梦的压倒性强者“假面骑士梦现”。莫与小鹰共同挺身对抗，却被逼入绝境。面对即将大白的恐怖计划，莫在走向崩溃的世界中做出了无情的决断。

Takeshi Hongo is a promising young man with a passion for motorcycle racing. However, his dreams are suddenly ruined when he gets kidnapped by Shocker, the evil secret organization planning to dominate the world. After being remodeled into a cyborg, Takeshi escapes and swears to protect the world from the inhuman monsters.

In a world shaped by the dreams we see in our sleep, Zeztz enters people's dreams as an agent on a mission. Equipped with a cutting-edge Rider belt worn across the chest, Zeztz brings a bold new form to the battle.