Yuta Hibiki wakes up in the home of his classmate, Rikka Takarada, with amnesia. A voice from an old computer, identifying himself as "Gridman," has a mission for him, but can he even survive the next day of school without his memories?

When the Tsutsujidai High School Festival is threatened, the Gridman Alliance must decide how to proceed. Some of them wonder if fighting is the only choice they have.