High schooler Yuta merges with Gridman to grow to super-size and defend his city from kaiju monsters with support from classmates Rikka and Utsumi. Their lives are disrupted when a kaiju suddenly attacks the city. Yuta fuses with Gridman again to fight the kaiju, and is assisted by the return of the Neon Genesis Junior High Students, who now count a newly revived Gauma as their newest member. But some unknown phenomenon is causing different universes to overlap.