A being calling itself "Hyper Agent Gridman" contacts high schooler Yuta through an old computer, recruiting him in the fight against impending terror.

Yuta Hibiki can't remember who he is, and now he's seeing and hearing things that others don't. A voice from an old computer tells him to remember his calling, and he sees a massive, unmoving creature in the distance. Nothing's making sense-until the behemoth springs to life. Suddenly, Yuta is pulled into the digital world, reappearing in the real one as the colossal hero-Gridman.