The Jashinka Empire is a clan of tailed people born from the underground evolution of life matter attached to a meteorite that fell to Earth long ago. In a culture where social status is determined by the number of tails, they have a strong desire to go above ground and plan to conquer it using scientific knowledge more advanced than that of humanity. They begin their invasion of the surface world by causing volcanoes to erupt all over Japan.

Scientist Yumeno Kyutaro, who sensed this, gathers five young scientists with exceptional intelligence and physical strength at the invention center he runs and establishes the Science Squadron. The five don Dynasuits, reinforced suits developed by Yumeno, and rise up as Dynamen to crush the ambitions of the Jashinka Empire.