Finishing up an important case, they beautiful bounty hunter Iria returns to Earth. Along with her computer, Bob, and her assistant, Fujicrow, she is also assigned an android trainee.

Unfortunately, the research team charged with building the android decided to implant the android with the most cunning combat life form in the universe, a vicious Zeiram unit! When the android is damaged during combat, it begins using the machine's wide variety of weapon systems to terrorize Iria and her old human friends, Teppei and Kamiya. All three of them are trapped in a dimensional Zone by the monster, and if anyone is going to get out alive, Iria will have to beat the monster one on one!