Keitarō Shinjō is a character who appears in the first two episodes of Robot Keiji. He is the older brother of Tsuyoshi Shinjō, a junior detective working in the Tokyo Special Crimes Unit. Keitarō was formerly a detective himself, but by the time of the series he has changed careers and works as a lawyer. His background as an experienced investigator means he possesses strong deductive and procedural knowledge, though his role in the story is limited to the introductory arc. He assists the police team in the early investigation of crimes linked to the criminal robot‑rental organization BAD, drawing on his past law‑enforcement expertise. His relationship with his brother Tsuyoshi is that of an elder sibling, but because his appearances are confined to the opening episodes, his character does not undergo significant development. His motivations are not explored in depth, but his shift from detective to lawyer suggests a continued dedication to upholding the law within a different professional capacity. No special physical or combat abilities are associated with him; his contributions rely on his investigative experience and legal knowledge rather than direct action.