Yōji is a young lonely factory worker who falls for an equally lonely girl co-worker, Sachiko, but is unable to tell her of his interest. After he is assaulted in a theater by a crossdresser, Yōji finds what looks like an alien insect and hides it in his room. The next night, he comes across Sachiko being sexually attacked by another fellow worker. He attempts to come to her aid but is beaten. Sachiko feels sorry for him and returns with him to his apartment. During this encounter, Sachiko is attacked by the alien object which penetrates her and turns her into a bio-mechanical monster, a NecroBorg. These parasites take over human bodies and use their flesh to create weapons which they use to fight each other. Yōji is also infected and the plot eventually leads to a showdown fight to the death between the two would-be lovers. A side plot concerns a father who is out to kill the NecroBorgs who have also infected his daughter.