Kawakubo serves as the dedicated butler to the young detective Narutaki in the anime Steam Detectives. His role is deeply rooted in a long-standing connection to the Narutaki family, as he was originally the butler for Narutaki's father. Following the tragic murder of Narutaki's parents by bandits when the boy was still a child, Kawakubo assumed the responsibility of raising and educating the young orphan. This formative period ensured that Narutaki could follow in his father's footsteps by opening his own detective agency.

Kawakubo’s personality is characterized by unwavering loyalty and a quiet, steadfast reliability. He manages the household and oversees Narutaki's personal affairs, providing a stable and supportive home base. Beyond these domestic duties, he is actively involved in Narutaki's detective work, offering crucial assistance in the laboratory with various research and experiments. His long history with the family also gives him a valuable perspective, as he is familiar with older cases from the father's time.

As an ally, Kawakubo is one of the most trusted members of Narutaki's team, which also includes the nurse Ling Ling and her giant steam-powered robot, Goriki. While Narutaki takes on the role of the active investigator, Kawakubo remains the anchor in the background, ensuring his charge has the resources and support needed to face the dangers of Steam City. His key relationship is undoubtedly with Narutaki, whom he serves and protects not just as a butler, but as a dedicated guardian who has overseen his upbringing from a tragic childhood into his career as a detective. There is no significant information available regarding notable combat abilities or a personal developmental arc for Kawakubo. Instead, his development is implied through his consistent, loyal service across generations.