After coming in contact with radioactive waste, small-time crook Enzo Ceccotti gains super-strength. A misanthropic, introverted brute, he uses his new powers for personal gain until he meets Alessia, a mentally ill girl who believes Enzo is the hero from her favorite anime Steel Jeeg.

Hiroshi Shiba is a car racer who is mortally wounded in a laboratory accident, but restored to life by his father, Professor Shiba.

Kenji Kusanagi, a high school student, becomes Kotetsushin Jeeg to fight the sudden reappearance of Haniwa Genjin from the Jamada Empire ruled by Queen Himika.