Toshio Otomo is a childhood friend within Yuu Morisawa's close-knit social circle. He remains unaware of Yuu's magical ability to become the teenage idol Creamy Mami. After Creamy Mami's television debut, Toshio develops a distinct romantic interest in her idol persona. This causes ongoing frustration for Yuu, who desires his genuine affection as her 10-year-old self.

In the OVA "Mahō no Tenshi Creamy Mami: Eien no Once More", set two months after Creamy Mami's final concert, Toshio participates when rumors emerge of her possible comeback. He collaborates with Yuu, Megumi Ayase, Midori Kisaragi, and Hayato Kidokoro to investigate these rumors and the nature of Shingo Tachibana's associated "Big Project". His actions are part of the collective group effort.

Toshio also appears in the OVA "Creamy Mami: Long Good-Bye".