Jin Kurono's father is dead, so he has been raised by his mother, who taught him the sense of honor and justice. But she died, killed by a car, with the culprit running away after the accident, leaving a scar on Jin's heart. Now, he's 23 years old, and the programmer of a new game called Zetman. Upset with the fact that there is no justice in the real world, he turns into his own superhero Zetman, to fight against crime, but with hard methods. To advise him and support him, he will always have his best friend, Sachiko Shirai.