"How much does it cost to launch a missile?" "How much does it cost to dry-clean the uniforms of combatants?" This is an "economically correct" robot hero story that has never been heard of before, with realistic themes as the point of view. A young technician, Tetsuro Okino, is sent to the pest extermination company, Hasuda Industries, with a new robot he developed, BULLBUSTER. What confronts Hasuda, whose president is Tajima, is a mysterious creature called "Giant Beast"! In addition, as a small company that is always short of money, Hasuda is always affected by economic problems... The fuel cost of the robot, the labor cost of the driver, and even the waste of a bullet are unacceptable. Caught between the "ideal" of exterminating the giant beast and the "reality" of cost, what will the future of Hasuda be?