Hideo is a Parasite with a teenager's body who decides to integrate with human society. Hideo enrolls in Shinichi's high school and expresses a desire to become friends with Shinichi, who does not trust him. Although Hideo is a relatively peaceful Parasite, he has no qualms about brutalizing or even killing bullies who try to start fights with him, and he continues to hunt humans (although he claims that he is learning to eat normal food instead).