Hosokawa Reiko forms one half of the idol pilot duo Fever Girls under Yajima Office management. At 20 years old during the series' primary events, she ages to 21 in the 1995 "Song of the Wind" timeline. She measures 163 cm tall with proportions of B94/W58/H84 and possesses waist-length wavy purple hair as her defining trait.

Reiko's Fever Girls unit maintains a professional rivalry with the Hummingbird squadron, accentuated by their overtly sexualized performances that highlight physical appeal. This includes coordinated public displays like vigorous lingerie-clad exercise sessions showcasing their physiques. The duo exhibits cattier, more jealous personalities compared to the Hummingbirds, fueling competition during events such as the Idol Defender athletic meet aboard the Enterprise carrier. There, their perceived superiority in physical allure becomes a recurring friction point.

Beyond aerial duties coached by Goro Kadou—a former associate of the Hummingbirds' missing father—Reiko's group prioritizes image-centric tactics. Their career revolves around visual presentation and audience engagement through meticulously staged physical exhibitions.