In the sequel to SSSS.GRIDMAN and SSSS.DYNAZENON, a year has elapsed since the events of SSSS.GRIDMAN. With the world now in a state of calm, only Rikka and Utsumi retain memories of the kaiju, Gridman, and Akane Shinjou. Surprisingly, even Yuuta, Gridman's former host, lacks recollection of his pivotal experiences. When a new Kaiju emerges, Yuuta seizes the opportunity to reaffirm his heroism by reuniting with Gridman, aiming to rediscover his purpose and past glory.