Kantaro Yotayama is the grandson of Kan-chan (Kanichi Yotayama), the original human protagonist from the 1969 Hakushon Daimaō series. He serves as the primary human companion to the genie family in the contemporary setting. Kantaro possesses fair skin, dark brown hair, black eyes, and a rounded face. His signature outfit features a red t-shirt displaying a distinctive white bottle pattern with blue eyes on the front—functionally concealing the magic bottle—paired with blue capris pants featuring side pockets, a light-green belt, white socks, and sky-blue loafers. He always wears a white-and-blue cap marked with a red "K" insignia representing his name.

Kantaro's journey begins when Princess Akubi emerges from the bottle for queenship training, sparking a series of adventures navigating modern life together. They undertake various jobs and confront everyday challenges, emphasizing themes of pursuing dreams and understanding human aspirations, which becomes central to Kantaro's growth. He evolves from an ordinary boy into a proactive participant in the genies' endeavors, showing adaptability and increasing responsibility.

A pivotal accident transports Kantaro into the genie bottle, revealing Akubi's true form as a tall, slender maiden. This exposure triggers an unspoken romantic attraction, complicating their dynamic. Though initially struggling with Akubi's dual appearances, his feelings deepen, adding emotional weight to their partnership. This subplot culminates in a parallel to his grandfather's unresolved relationship with Yuriko: Kantaro attempts to confess his feelings, but external forces—the genies' inevitable separation from the human world due to their binding magic—prevent a lasting union. Despite his efforts to keep the bottle, a farewell ensues, underscoring themes of impermanence and maturity.

Kantaro also interacts with Akubi's family: Hakushon Daimaō (King Genie), whose magic often backfires comically, and her younger brother Pūta, summoned by flatulence. These relationships highlight Kantaro's role as a stabilizing influence amid the genies' chaotic tendencies. His character arc concludes by emphasizing personal growth through loss, mirroring his grandfather's experiences while affirming the transient yet impactful nature of their extraordinary bond.