A thousand years from now, artificial humans live peaceful lives on Neoterror, a terraformed world where AI has rebuilt the lost civilization of Earth. Tarou is a somewhat introverted boy who would rather not do much of anything. Then he encounters a strange being called Tamagar, which grants him the power to become the relentlessly upbeat hero Gainaman. With these abilities he sets out to resolve incidents around the city. His stylish younger sister Hanako pleads with Tamagar for powers of her own and joins him as Gainaman No. 2. Meanwhile, Ai-chan, an android interface serving the bureau that oversees the AI, secretly works with her partner Rakkyo-boy to catch Tamagar. The result is a short sci-fi hero story released online.