G4 is a very large and stocky humanoid robot. His equipment is lavishly decorated with shiny ornaments and plating, and he even wears a royal fur cape and crown. G4 is there to test his combat AI with the objective assigned to him. his attitude is cold, serious and sometimes arrogant. G4 was looking for his target called "King" who is an S-Class of the Hero Association who call him the "strongest man in the world". G4 is faithful to the Organization and follows the orders of the Organization.