TV-Series
Description
Keiichirou Aoyama is one of the three main pilots of the giant robot Dai-Guard, serving as the machine's engineer. He is a 25-year-old salaryman working in the Public Relations Division 2 of the 21st Century Defence Security Corporation, having graduated from Hokkaido University of Technology alongside his fellow pilot, Shunsuke Akagi. Initially, his primary motivation for joining the company was not a sense of justice or a desire to pilot a giant robot, but a practical one: he believed the job offered good pay for the amount of free time it would allow him. This was because Aoyama bears a significant personal responsibility: he is the sole caregiver for his sick mother.

On the surface, Aoyama presents a cool, collected, and somewhat aloof demeanor. He is known for being a ladies man and carries an air of mystery, often vanishing immediately after work and leaving his colleagues to speculate about his romantic pursuits. In reality, his mysterious disappearances are to visit and care for his ailing mother, a secret he keeps to himself for a considerable time. This tendency to not confide in his peers often leads to misunderstandings, but he is not a hot-headed character. Instead, he is known for being calm and level-headed, rarely taking the initiative in arguments but consistently finding ways to resolve problems when they arise. His personality forms a stabilizing counterpoint to the more passionate and impulsive Akagi.

Within the operational structure of Dai-Guard, Aoyama's role as an engineer is critical. He is responsible for regulating the robot's fuel flow and power output, a task he performs with clockwork proficiency. His absence from the cockpit has a noticeable effect on Dai-Guard's performance, drastically slowing its speed and hindering its ability to perform evasive maneuvers, whereas the other pilots have more redundancy in their functions. True to his nature, he is always seeking ways to save time and effort, which translates into an intuitive ability to identify the most efficient method for the team to accomplish a given goal.

Aoyama's key relationships evolve significantly throughout the series. He initially works alongside his two fellow pilots, the enthusiastic Shunsuke Akagi and the determined Ibuki Momoi, but remains somewhat detached due to his secret obligations. His reluctance to fully commit to piloting Dai-Guard becomes a point of internal conflict, which is eventually challenged by his mother herself, who does not wish to be his top priority over his duties. Her criticism pushes him to fully embrace his role as a pilot. He also develops a close relationship with his colleague Chiaki Nakahara, who learns of his circumstances and becomes a source of support, with hints of a deeper romantic connection forming between them. His past also resurfaces when he encounters an ex-girlfriend, Arisa, which reveals more about his history of balancing personal sacrifice with his responsibilities.

Unlike his fellow pilots who represent more traditional growth from inexperience, Aoyama is characterized by the resolution of existing conflicts rather than learning new skills from scratch. His development is marked by his transition from a reluctant participant, whose primary concern is caring for his mother, to someone who openly admits that he is fighting to protect his colleagues and the simple, everyday moments of life. While he is not the most vocal member of the team, his quiet competence, deep-seated loyalty, and humanity make him an indispensable part of the trio that defends the world in the giant robot Dai-Guard.