The character known as Chachamaru Master is the owner and bartender of the Chachamaru bar, a modest establishment that serves as a central gathering place for the residents and regulars of Maison Ikkoku. His background is largely undefined, and his real name is never revealed in the series, as Master is simply the title given to someone who runs a bar of this kind. The bar itself, described as unremarkable in appearance, is where a significant portion of the social action takes place, largely due to the presence of its other employee, the waitress Akemi Roppongi.

In terms of personality, the Master is portrayed as a reserved and easy-going individual. He maintains a calm and patient demeanor, notably allowing his waitress Akemi to be as lazy as she wishes while she is on the clock. However, this laid-back attitude does not preclude a shrewd side; when it pertains to the business aspects of running Chachamaru, he is perfectly capable of being pragmatic and economical to save money. His central motivation appears to be the steady operation of his bar, serving cold beer and snacks to his patrons, but he also shows a clear, if understated, investment in the well-being of his regular customers.

His role in the story extends beyond simply providing a setting for drinking. The Master serves as a quiet, stabilizing presence amid the often chaotic lives of the Maison Ikkoku residents, including the protagonist Yusaku Godai and the manager Kyoko Otonashi. He occasionally intervenes directly in their affairs. For instance, when other patrons drunkenly tell Kyoko exaggerated and false horror stories about Godai's activities, the Master takes it upon himself to clarify the situation and set things right. His most prominent storyline involvement occurs during the formation of a baseball team, where he takes the initiative to organize a team composed of his best patrons to compete against local businessmen, leading to comedic results given the unconventional nature of his players.

Key relationships are primarily centered on his bar. He has a professional and tolerant relationship with Akemi, whom he employs as a waitress, allowing her considerable freedom. He is also a consistent presence for the regular group from Maison Ikkoku—including Godai, the gossipy Mrs. Ichinose, and the mysterious Yotsuya—providing them a place to unwind and, often, to become completely intoxicated. While he does not undergo a dramatic personal transformation over the course of the story, his development is shown through his growing, subtle investment in the romance between Godai and Kyoko, acting as an occasional mediator. The Master does not display any flashy or unusual abilities; his notable skill lies in his quiet perception and his capability to be tactfully meddlesome when the situation calls for a level-headed figure to restore order or honesty among his drinking establishment’s clientele.