From what I have gathered, Iria: Zeiram is a prequel to an earlier live action series.

Iria is a deputy bounty hunter working for her older brother. They are brought along on a hostage rescue, only to face an unkillable monster named Zeiram. Iria is the only survivor of the battle -- maybe. Her brother gives his life to destroy Zeiram -- maybe. Zeiram has been obliterated in the explosion of a spaceship – unlikely, as that would end this OVA with the first episode, and there are five more to follow.

There are a lot of action scenes jammed into this anime, as Iria and friends just can’t seem to shake Zeiram off their tail. Unfortunately, six episodes means the story-line is pretty thin, character development gets no more than a token effort, and maybe a plot hole or two develop. If you are looking for some slam-bam-boom action without being given anything to think about, Iria: Zeiram is for you. Just note that this anime is from the early 1990’s, so the animation is a few steps below what we are used to today.