Doctors Kazamatsuri and Onizuka are geneticists researching cures on diseases such as AIDS and cancer by performing experiments to strengthen the human body. The test subject is Shin Kazamatsuri, motorcycle racer son of Doctor Daimon Kazamatsuri. Unknown to them, their operation is funded by a syndicate group, who plan to use this research to have the bodies of men strengthened for their own gain—they have already been experimenting in the field of cyborg soldiers, to a less-than-successful attempt. However, they didn't count on Onizuka's own secret ambitions. The mad Onizuka wanted to create a new species, by fusing a grasshopper's DNA with the test subject's own DNA, in order to start a new civilization and be their god. Onizuka tested on himself, but seems to be having greater success with Shin.

Meanwhile, a murderous creature is stalking the city and it haunts the dreams of Shin. While he believes he is the one causing the murders, he eventually finds out about the plan of Onizuka and discovers that it is Onizuka is who is responsible for the murders. Onizuka has experimented on himself and altered his genes, making him a humanoid grasshopper. The telepathy of grasshoppers allowed him to communicate with Shin, resulting in his witnessing the murders through his dreams. The syndicate learns of Onizuka's plans and have him institutionalized. As if the syndicate were not enough, a CIA agent tracks down Shin and wants him eliminated, for he doesn't know the true threat he could pose. The repulsed Shin digs to find out all he can about the experiment he foolishly volunteered to be a part of, which is now altering his body and putting him and his loved ones in danger.