Ichiro Okinoshima is a recurring character in GTO who serves as the talent manager for the aspiring teen idol Tomoko Nomura. At twenty-six years old, he works for the production company Goblin Productions, having previously been affiliated with Pink Elephant. Before entering the entertainment industry as a manager, Okinoshima was the president of the Teen Idol Research Club during his time at Meiji University. His professional experience also includes managing other talents, such as the enka singer Ryoko Todoro and Hiroe Onuki.

Okinoshima is deeply infatuated with Tomoko Nomura and is wholly committed to her career and personal well-being. His primary motivation is a fervent dream to see Tomoko rise to become the top teen idol in all of Japan. This dedication manifests as an obsessive protectiveness, and he is particularly diligent in defending her modesty and reputation from what he perceives as threats, most notably from the photographer Munakata. His role in the story is intrinsically linked to Tomoko, acting as her guardian and promoter within the competitive and often seedy world of the entertainment industry. Later in the series, his responsibilities as a manager expand when he also begins to manage another character, Mayu Wakui, in partnership with his former rival, Munakata. This partnership indicates a degree of professional development and a willingness to collaborate for the sake of his charges.