One fateful day, high school freshman Yomogi Asanaka stumbles upon a famished stranger named Gauma beneath a bridge. Gauma, a self-proclaimed 'kaiju user,' reveals his role in combating city-endangering monsters. The next night, Yomogi crosses paths with Gauma and his classmate Yume Minami as a kaiju emerges in the urban landscape. In a moment of crisis, Gauma unveils a mystical artifact from a radiant pouch, summoning the colossal robot Dynazenon. To pilot this mechanized warrior, four individuals—Gauma, Yomogi, Minami, and Koyomi Yamanaka, a jobless wanderer—are drawn into its cockpit. This event sparks their involvement with nefarious kaiju-controlling foes known as kaiju eugenicists, propelling them on a quest to unlock Dynazenon's true power.