Hideo Shimada (島田 秀雄, lit. Shimada Hideo) is a parasite with a teenager's body who decides to integrate with human society. He worked with Reiko Tamura to study Shinichi Izumi and Migi.
In the manga, Hideo is a young man of slightly above average height, with wide-set shoulders and a generally sturdy build. He has heavily pointed eyes, with wide, flat eyebrows. His hair is neck length and black, with two short bangs at the sides of his forehead.
In the anime, he is slightly smaller, with a lankier build. He had brown hair and light brown eyes. He has a pointed fringe, which spikes down in the middle of his forehead. He wears the same school uniform as Shinichi, which consists of a white shirt and a blue blazer, while in the manga he wears a white shirt with black suit pants.
When he made his first appearance, Hideo revealed himself to be a relatively peaceful Parasite. After being confronted by Shinichi and Migi, he claimed he had no intention of harming Shinichi or anyone in his school and was more interested in getting to know the two of them.
Despite this, it was revealed that Hideo held no qualms with brutalizing or even killing bullies who tried to start fights with him and continued to hunt humans despite his claims to Shinichi that he was learning to eat normal food instead.
He is an active sports player, and states that it helps him get better at controlling his human host body.