Taihei Hiraga, a Japanese zoologist and father of Taichi Hiraga-Keaton, wed Patricia Keaton, an Englishwoman of distinguished background. Their marriage dissolved when their son turned five, with Taihei remaining in Japan while Patricia returned to England with Taichi—a separation echoing Taichi’s own later divorce, as both men faced spousal departures and the loss of custody over their children.

Known for his roguish charm and penchant for pursuing younger women, Taihei’s romantic escapades frequently land him in precarious situations, from financial strain to brushes with organized crime, notably a botched scheme involving a purloined Bengal tiger and the Chinese mafia. Yet beneath his mischievous exterior lies a genial, lighthearted soul, often seen with his steadfast companion Taisuke, a Chow Chow–St. Bernard crossbreed renowned for his uncanny olfactory prowess.

His dynamic with Taichi blends warmth and friction, their contrasting natures—Taihei’s free-spirited impulsiveness against Taichi’s restrained pragmatism—sparking both conflict and camaraderie. Shared visits to their ancestral Japanese home stir echoes of Patricia and the family’s splintered past, while Taihei’s playful, if haphazard, grandfatherly efforts toward his granddaughter Yuriko reveal his enduring, if flawed, devotion.

Though chiefly a secondary figure, Taihei occasionally plunges into investigative intrigues, drawing on his zoological knowledge or eclectic network. His arcs weave themes of aging, remorse, and the fragile tapestry of kinship, mirroring Taichi’s journeys through generational echoes of fractured relationships and resilient, if complicated, love.