Kotaro Higashi begins as a wandering adventurer returning to Japan aspiring to box. He aids defense team ZAT near a Tokyo port, immobilizing the monster Oil Drinker with a crane. Shortly after, Tigris Flowers he planted mutate into the monster Astromons, which kills Oil Drinker and attacks the city. Kotaro suffers fatal injuries confronting Astromons. The Ultra Brothers transport his body to the Land of Light, where Mother of Ultra and the Ultra Brothers merge his life essence with Ultraman Taro, reviving him. This fusion enables Kotaro to transform into Ultraman Taro using an Ultra Badge gifted by Mother of Ultra, who appeared as the Lady in Green. Joining ZAT, Kotaro combats monsters while residing with Captain Shiratori's family, bonding with Shiratori's children, Saori and Kenichi. His initial recklessness matures into disciplined courage through battles against adversaries like Birdon—a monster that temporarily kills Taro and Zoffy before their revival by Father of Ultra—and the composite monster Tyrant. Mother of Ultra occasionally guides Kotaro through visions, including forewarning Captain Shiratori's death during Samekujira's attack. The emotional fallout causes Kenichi to resent Ultraman Taro, prompting Kotaro to reveal his identity. To affirm his faith in human resilience, Kotaro returns the Ultra Badge to Mother of Ultra, severing his transformation ability. He subsequently defeats Alien Valky—who attacks believing Taro remains—using human ingenuity by luring the alien into an oil refinery and igniting it with a ZAT weapon. This victory concludes his ZAT tenure, and he departs to travel the world as an ordinary human. The 1984 film *Ultraman Story* retcons Taro's origin, depicting him as a distinct Ultra being raised from infancy on the Land of Light by Father and Mother of Ultra. This version details his childhood, training, and early battles against Juda and Grand King before being dispatched to Earth. The film omits Kotaro Higashi, establishing Taro as a separate entity who later merges with Kotaro during the 1973 series events. This retconned backstory became Taro's basis in subsequent media, voiced by Hiroya Ishimaru, diverging from the series' initial ambiguity about their unification. After Kotaro relinquishes the Ultra Badge, Taro resumes activities in the Land of Light as an Ultra Coliseum instructor. He mentors younger Ultras like Ultraman Mebius and fathers Ultraman Taiga. He aids allies during crises, such as restoring Earth's sunlight in *Ultraman Mebius & the Ultra Brothers* and combating the revived Dark Four Heavenly Kings in *Ultraman Mebius Side Story: Ghost Rebirth*. Prose stories explore his history with scientist Tregear, a childhood friend turned antagonist, revealing their joint adventures on Planet Tika-Du and Tregear naming the Taiga Spark device intended for future generations. In the *ULTRAMAN* manga continuity, Kotaro Higashi is reimagined as a Japanese photographer investigating alien activity in America. Alien Druz fatally wounds him, but alien chemicals resurrect him, granting superhuman strength, speed, and durability. Adopting the alias "Taro," he crafts a makeshift superhero suit and allies with the SSSP. His abilities evolve into a volatile "Flame State," requiring a specialized suit built by Yapool for control. This Kotaro engages in conflicts like the battle against the Star of Darkness in New York and investigates human-alien tensions, notably clashing with alien Valky. Unlike the original series, he retains his powers and continues operating as a superhero within the manga's narrative.