Kazuma Tamura is an eight-year-old second grader at Gekkō Elementary School in the fictional Moonlight Town. The only child of Makoto and Ai Tamura, he shares a close bond with his inventive grandfather, Tomio "Tommy" Tamura, who lives separately in a log cabin.

Physically, Kazuma has light skin, black spiky hair, and distinctive diagonal lines on each cheek. He typically wears a light blue short-sleeved shirt with a "V" emblem, shorts, and white shoes featuring blue laces.

Gentle, kind, and obedient by nature, Kazuma possesses a strong enthusiasm for athletics, especially soccer. He diligently maintains a dedicated rock collection in his room; his passion for geology leads to irritation when others disregard or mishandle his specimens, as when Ojarumaru sat on them. He also harbors a fear of dogs.

Kazuma's life changes when he discovers and befriends Ojarumaru, a time-displaced Heian-era prince. He convinces his parents to let Ojarumaru live with them, forging a brotherly bond. Kazuma often transports Ojarumaru on his back or backpack during outings. Together, they collaborate on strategies to evade the Kooni Trio's attempts to reclaim King Enma's scepter.

His traits are further shown when a fever motivates Ojarumaru to seek Heian-era herbs, and when Kazuma tries singing lullabies to soothe Ojarumaru's insomnia. He participates in beach visits and summer festivals with Ojarumaru and classmates.

Kazuma interacts with classmates like the wealthy, lollipop-loving Kintarō "Kin-chan" Sakata and fashion-conscious Komachi Ono. He respects his grandfather Tommy's pursuits and appreciates his mother Ai's nurturing role.