Bio-noid No. 18, developed and operated by the Federal Investigation Agency, is an artificial investigator equipped with a state-of-the-art plasma engine, possessing exceptional durability and combat capabilities for diverse mission profiles. He has operated in a secluded forest laboratory, eliminating dangerous individuals who modify their bodies and create various bio-creatures. However, during his escape from the facility, he is attacked by a massive leech-type bio-creature targeting his plasma engine.