Kisou Kobayashi, often called by the nickname Koba, is one of the elderly tenants living in the seaside housing complex at the center of the story. His background suggests he was a man of many practical skills, as he describes himself as a handyman or tinkerer who has fixed everything from common household appliances to large naval warships. This detail points to a long and varied working life, possibly including experience in repair, engineering, or military maintenance. In his personal life, his wife resides in a separate rest home, indicating that he lives alone in the complex while she receives care elsewhere.

In terms of personality, Kobayashi is portrayed as a friendly and doting figure, particularly towards the complex's young protagonist, Kimi. Like the other older residents, he shows great affection for her and is often seen keeping a watchful eye on her. He is a social member of the community and is frequently seen in the company of his contemporaries, including other elderly tenants named Taka and Yoshiken. His demeanor is one of a seasoned and capable individual, likely stemming from his past as a tinkerer, and he takes a practical approach to the bizarre events that begin to unfold in the complex.

Kobayashi's primary motivation is rooted in the well-being of his small community, with a particular focus on protecting Kimi. When strange incidents start occurring, from dead animals appearing to tenants mysteriously vanishing, he does not simply stand by. He puts his experience to use as part of the group's efforts to understand the threat. His role in the story is that of a supportive elder and a proactive member of the community who joins the search for answers. He is among the older residents who accompany Kimi as they explore the ancient ruins located beneath the housing complex, hoping to find the source of the malevolent force that is plaguing them.

Kobayashi's key relationships are with his fellow long-term residents. He shares a strong bond of camaraderie with Taka and Yoshiken, and together they represent the older generation who have lived in the complex for an extended period. His most significant relationship, however, is with Kimi, whom he treats with warmth and protectiveness, acting as a grandfatherly presence in her life. Throughout the story, his development is shown through his shift from a quiet, affable resident to an active participant in the confrontation against the ancient evil. He uses his practical knowledge and his familiarity with the complex to assist in the investigation, demonstrating that his skills as a tinkerer are valuable even in the face of supernatural horror. His notable abilities lie in his practical, hands-on expertise and his willingness to act, proving himself to be a reliable and resourceful figure in a crisis.