The OVA will be based on the Narumi Seo character map story event that was featured in the smartphone game in April 2018. Seo, who has a unique memory disorder, will appear alongside other heroes of the Seo Research Laboratory in the OVA.

Theatrical follow-up to Sasaki to Miyano, adapting the "Graduation Arc" of the manga. Miyano’s world of Boys’ Love manga turns to reality when chance leads him to Sasaki. Now, Sasaki wants to spend every opportunity with him.

After their world was saved by Gridman and Akane Shinjo returned to the real world, Yūta, Rikka, and Utsumi return to their normal lives, though Yūta still has to adjust to losing two months of his memories due to being possessed by Gridman during that time. Rikka and Utsumi work on writing a script for a play their class will perform in the upcoming school festival based on their experiences with Gridman, while Yūta tries to work up the courage to confess his feelings to Rikka. However, their life is disrupted when a kaiju suddenly attacks the city. Yūta voluntarily 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 who commands DynaRex as their newest member. Gridman and the NGJHS defeat the kaiju, and explain that some unknown phenomenon is causing different universes to overlap in a potential Big Crunch.