Tomio Tamura, widely called Grandpa Tommy, serves as Kazuma's paternal grandfather and Makoto's father. At 70 years old, he lives in a log cabin detached from the main Tamura residence. A historian by profession, he specializes in studying ancient folk tales and fairy tales, with academic pursuits centered on Great King Enma's culturally significant scepter.

He crucially aids Ojarumaru's transition to modern life, leveraging his Heian-era expertise to convince Makoto and Ai to shelter the displaced prince. This historical knowledge helps interpret Ojarumaru's origins, bridge cultural gaps, and mediate his interactions with others.

Tommy passionately invents functional mechanical robot dolls, such as the behavior-altering "Mechanical Music Doll" and dessert-producing "Mechanical Dessert Doll." These creations frequently trigger episodic adventures.

His past includes a courtship with his late wife, Sayuri "Sally" Tamura, complicated when her sister Mariko manipulated their communication to arrange their marriage—a history revealed through flashbacks and family photographs.

Consistently supportive and intellectually driven, Tommy investigates the scepter's mysteries and Ojarumaru's Heian ties while nurturing familial bonds. He mentors Kazuma during the prince's escapades and provides essential historical context that deepens other characters' comprehension of unfolding events.