Daijiro Ohara is the Chief Patrol Officer ("Buchō") commanding the police box stationed before Tokyo's Katsushika Ward's Kameari Park. He directly supervises officer Kankichi Ryotsu. Ohara embodies the seasoned middle-management police officer, regularly venting frustration and exasperation over Ryotsu's characteristic laziness, neglect of duty, and pursuit of money-making schemes, often resulting in disciplinary actions. Despite this stern oversight, Ohara occasionally reveals genuine care for Ryotsu, treating him almost like a son. He extends this paternalistic concern to other officers under his command, including Reiko Akimoto and Keiichi Nakagawa, functioning as a father figure within the police box.

Ohara sports a notably small, trimmed mustache. His personal interests include traditional Japanese pursuits like judo, kendo, tea ceremony (sado), bonsai cultivation, and calligraphy. He commutes using public transportation, specifically bus and train services. Outside work, Ohara is married with one daughter, Hiromi, and is a grandfather to Hiromi's two children. His background connects him to the working-class districts of old Tokyo, aligning with the series' focus on Shitamachi culture. His role remains consistently defined by his supervisory position, balancing discipline with paternal concern amidst the police box chaos.