The root of all evil lies in Chuunibyouji (eighth-grader syndrome). Every delusion, crime, and psychic phenomenon in this world began with chuunibyou-sickness. The dark energy of chuunibyou-sickness, causes the craziest incidents.

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!