Tamager, a mysterious life form of unknown origin, resembles a sentient egg capable of granting transformation powers to create superheroes. Concealed among ordinary eggs, it is discovered by protagonist Taro. Upon contact, Tamager bestows upon Taro the ability to become the superhero "Gainaman," providing him with special powers to address incidents in their city. Tamager later grants similar transformation capabilities to Hanako, Taro's younger sister, enabling her to become "Gainaman No. 2" and support her brother's missions. Throughout the series, Tamager's true nature and motives remain unclear, maintaining its enigmatic presence. This existence attracts pursuit from the AI management bureau, specifically the humanoid terminal Ai-chan and her partner Rakkyo-boy, who seek to uncover Tamager's secrets.