Taihei Hiraga, a Japanese zoologist, married Patricia Keaton, a well-born Englishwoman, and fathered a son, Taichi Hiraga-Keaton. The couple separated when Taichi was five, leading Patricia to return to England with their son while Taihei stayed in Japan.

Renowned for his zoological expertise, Taihei owns Taisuke, a Chow Chow–St. Bernard mix dog with an extraordinary sense of smell that exceeds typical canine abilities. Taisuke occasionally participates in Taihei's professional activities, highlighting the zoologist's connection to animals.

Despite geographical distance, Taihei maintains a relationship with his son Taichi, though his womanizing tendencies provoke blunt or sarcastic responses from Taichi. Taihei independently involves himself in investigative mysteries, extending beyond his academic work. He also interacts with his granddaughter Yuriko, though details of their dynamic remain sparse.

Noted for his lack of domestic prowess, particularly in household management, Taihei embodies an unconventional father figure. His independent pursuits include investigative endeavors that sometimes intersect with his son's cases.

Within narratives, Taihei emerges when his zoological background or family ties become relevant, such as during investigations of animal anomalies or familial mysteries. He consistently functions as a supporting character whose actions occasionally influence or overlap with primary plotlines, especially those involving Taichi.