Yosuke Nakamori is the grandfather of protagonist Mai Kazuki and co-leader of the stage magic troupe Magic Carat, sharing leadership duties with his wife Haruko Nakamori. He maintains a close bond with Mai, actively encouraging her dream of becoming a magician despite her early struggles. Within Magic Carat, Yosuke performs and helps organize the troupe, though substantive decision-making authority primarily resides with Haruko. His supportive presence extends beyond family, providing paternal guidance to younger troupe members Yukiko Hirota, Susumu Siozawa, and Akira Matsuo.

A key moment arises when Yosuke entrusts Mai with a heart-shaped mirror during a move, an act that inadvertently enables her encounter with the mirror fairy Topo and triggers Mai's acquisition of magical abilities. Throughout the series, Yosuke remains a steady participant in the troupe's activities, supporting Mai as she navigates her magical identity alongside her pursuit of authentic stage magic skills. This consistent role continues in crossover OVAs like "Adesugata Mahou no Sannin Musume" and "Majokko Club Yoningumi A-Kukan Kara no Alien X," where he appears alongside other magical characters within the context of magical performance.

Across the primary series, OVAs, and related media, Yosuke's character does not undergo significant personal backstory, evolution, or development beyond his established roles as a supportive grandfather and troupe co-leader. His characterization consistently emphasizes stability and encouragement within both the family and the professional magic troupe environment.