Yoichi Terai works as a patrol officer at the Kameari Park police station. He appears as a middle-aged man with a chubby build and curly dark brown hair, typically seen wearing circular glasses that frequently obscure his eyes. His standard uniform includes a blue suit, white undershirt, blue pants, black tie, and black shoes; he shortens the sleeves during summer. Terai maintains a grounded and neutral demeanor, offering a realistic perspective distinct from his colleagues' extremes, devoid of overt greed or anger. While diligent and responsible in his routine duties and casual conversations, he exhibits sensitivity and occasional indecisiveness under pressure. This reliability earns the trust of his superior, Daijiro Ohara, who often tasks him with reporting on Kankichi Ryotsu's whereabouts after disruptions. Terai occasionally brings small snacks or items of interest to share. Professionally, Terai attempts to dissuade Ryotsu from scams or money-making schemes, though his sensitive nature sometimes leads him to yield to Ryotsu's persistence out of apprehension. He shares a respectfully casual relationship with Keiichi Nakagawa, addressing him as "Nakagawa-kun." Terai commutes daily by train, resulting in developed rail system knowledge. His personal interests encompass hobbies like oil painting and calligraphy. During the events of the 1999 film adaptation, Terai participates in a simulated bank robbery exercise with Ryotsu. Forced into an uncharacteristically active role, he reluctantly follows Ryotsu's unscripted escalation of the drill, including enduring a paint dye bomb detonation. Terai utilizes a Smith & Wesson Model 15 revolver during this sequence. He was born in Hokkaido and is the father of two sons.