Hiromi Tachibana is a sixth-grade student at Harukaze Elementary School who pilots the Land Stego, one of three components forming the primary mecha Gosaurer. He also serves as a secondary pilot for Gosaurer and its upgraded form, King Gosaurer. His mother, Sayoko Tachibana, works as a doctor, while his father remains unmentioned. Hiromi displays a timid and inoffensive personality, frequently reluctant to engage in piloting duties yet consistently proving reliable during critical moments, embodying the Cowardly Lion archetype. Within the team dynamic, he represents the Superego, counterbalancing Kenichi Minezaki's impulsive Id and Shinobu Asaoka's hot-tempered Ego.

Academically, Hiromi is a budding mangaka and designs the Saurers team logo. His hobbies include writing and drawing manga, and he occasionally stalks classmate Kumiko Tanabe for manga illustration material, implying a potential romantic interest. He is also skilled at cooking. Key episodes explore his development: Episode 3 examines his initial hesitation to join the Saurers; Episode 14 delves into his relationship with his mother; and Episode 31 follows his attempt to create a manga based on his piloting experiences, highlighting his evolution from reluctance to dedicated teamwork.

Hiromi operates alongside classmates Kenichi Minezaki (pilot of Mach Ptera) and Shinobu Asaoka (pilot of Thunder Brachio). Their mechas combine to form Gosaurer, with Land Stego constituting the chest and head section. As part of the Saurers team, Hiromi contributes to defensive operations against the Mechanization Empire, though his prominence decreases after auxiliary pilots Kinta and Youji join and assume larger roles. Unlike Kenichi, Hiromi avoids roboticization or direct combat curses.

Appearances in other media such as movies, OVAs, or spin-offs are not documented for Hiromi Tachibana.