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?

Yuta and his friends attempt to unravel the mystery of the city and everyone else's memories. However, more questions arise when a strange samurai arrives and tries to tamper with Gridman.

A new kaiju appears which poses a problem for Yuta and Gridman. As a result, Rikka and Utsumi are left wondering if their friend will end up long since dead, just like the other students.

Rikka and Akane are invited on a group date, but the aftermath is disastrous. Will Yuta be able to convey his feelings for Rikka before it's too late?

A field trip takes the class away from the city for some summer fun, but when trouble occurs so far from home, there's no easy way to get to Junk.

A few unexpected encounters leave Yuta and the others in shock. Except, Gridman being hunted down means Yuta is ever in danger.