Kouichi is a junior-high school student who dreams of being a hero someday. One day he encounters an accident in which a gigantic humanoid called “LINEBARREL” falls right out of the sky. He subsequently becomes what people refer to as a “Factor”, a pilot of the mecha whose life goes hand-in-hand with the life of the mecha he pilots.
Kouichi obtains extraordinary physical strength as a result of becoming a Factor. This drastic change gives Kouichi excessive confidence, making him arrogant and aggressive.