Spunky Iria had always admired her older brother. He was the best bounty hunter there was. He was her mentor and her only family. As an apprentice bounty hunter, Iria accompanies her brother and his boss on a mission to rescue a VIP and retrieve a mysterious cargo. Trouble starts when it is discovered that the cargo is Zeiram - a seemingly invincible creature for use as a bio-weapon. Things take a turn for the worse when Zeiram breaks loose and starts destroying everything in sight. Iria finds herself caught between Zeiram and a major conspiracy. Now it's up to Iria to untangle everything and stop Zeiram.