Kaoru Orizuka serves as the department manager and direct superior to the protagonist, Saku Fukuzawa, at the company where both are employed. In his early thirties, Orizuka is a handsome man with slightly spiky black hair and distinctive silver-blue eyes, and he is known for consistently wearing a neutral, unreadable expression. He is highly regarded within the workplace as a competent and capable individual, though the combination of his immaculate appearance and reserved demeanor has led to office rumors that he might be a germaphobe.

Personality-wise, Orizuka is characterized by a stoic and cool-headed nature. He is a man of few words and fewer emotional displays, preferring to observe and analyze situations quietly. Despite his cold exterior, he demonstrates a strong sense of responsibility, particularly towards his subordinates, and possesses a high level of social competence, as evidenced by his ability to regularly attend drinking parties with company executives. This professional reliability makes him well-regarded by his team, even if he maintains a certain emotional distance.

Orizuka's primary role in the story is closely tied to his subordinate, Saku. He is one of the few people who suspect that Saku's flawless performance at work may not reflect her true nature. Approximately three years prior to the main events of the series, Orizuka witnessed the reality of Saku's life when he drove his intoxicated subordinate home and saw her apartment in a state of complete disarray. This incident formed the basis of his persistent, though unspoken, concern about her ability to live alone. He has vague knowledge that Saku owns a cat, but due to the logical impossibility of a small feline growing to an enormous size, he operates under the mistaken belief that the giant, bear-like Yukichi is simply Saku's close friend rather than her pet. Orizuka chooses not to directly confront Saku about these discrepancies, respecting her enough to understand that she is not a liar or someone who seeks attention, and therefore he finds no need to pry into her private affairs.

His key relationships extend beyond the office. He is the uncle of a young girl named Yume, who is often left in his care by his older sister. Despite openly stating that he does not particularly like children, Orizuka dutifully looks after Yume, and his interactions with her on outings, such as a trip to the aquarium, reveal a more patient and caring side to his personality. Within the Fukuzawa household, Orizuka shares a unique dynamic with the cat Yukichi. Having encountered Yukichi years ago as a small kitten who seemed to apologize for Saku's behavior, Orizuka dismissed the memory as a drunken hallucination and remains unaware of the cat's true, housekeeping masterfulness.

Throughout the narrative, Orizuka shows subtle signs of development in his perception of Saku. While he remembers her as a timid and somewhat hopeless individual from the time of her hiring, he has come to acknowledge her remarkable transformation into a highly effective and polished office lady. Recognizing the positive change in her, he continues to watch over her with a quiet, protective eye, particularly during company social functions where he monitors her drinking pace, silently ensuring she does not repeat the incident of three years prior. His notable abilities lie not in physical prowess but in his sharp observational skills, professional competence, and the capacity for silent, unwavering support that borders on the paternalistic, all while maintaining a façade of detached professionalism.