Toshio Ohtomo is a middle school student in Kurimigaoka who attends St. Remy Academy Middle School. He maintains a close childhood friendship with Yu Morisawa and Midori Kisaragi. Toshio initially holds an unexpressed affection for Yu, struggling to recognize or act on these feelings. After Yu accidentally debuts on television as her transformed 16-year-old idol persona, Creamy Mami, Toshio becomes intensely infatuated with the idol, unaware of her true identity. He frequently attends Creamy Mami's concerts and appearances as her most devoted fan, creating a complex dynamic where his idol admiration overshadows his connection to Yu in her everyday form.

In episode 25, Toshio witnesses Yu transforming into Creamy Mami, causing Yu to lose her magical abilities. To restore her powers, they journey to Feather Star, where the alien Pino Pino offers to reinstate Yu's magic if Toshio's memory of the transformation and magic is erased. Toshio agrees. Later, he discovers a recording of the incident, triggering the return of his suppressed memories. By episode 47, Toshio fully comprehends that Creamy Mami and Yu Morisawa are the same person, realizing his genuine feelings for Yu transcend his idol worship.

Toshio appears in OVAs including *Eien no Once More*, *Lovely Serenade*, *Long Goodbye*, and *Curtain Call*, where his role remains consistent with his established relationships and the understanding gained by the series' conclusion, without new character development or narrative progression. The manga released alongside the TV series features him but adds no additional backstory or development beyond the anime.