Mazuru Ameku is the older sister of Takao Ameku, the main protagonist of Ameku M.D.: Doctor Detective, and serves as the administrative director of Tenikai General Hospital. She is thirty years old and has long black hair that she typically wears tied back in a ponytail, along with blue eyes. Her usual attire consists of an ash-gray business suit and black dress shoes. As the hospital administrator, Mazuru is responsible for the smooth operation of the facility and is notably the only person who can effectively manage and control her brilliant but highly eccentric sister Takao. Her personality is strict and no-nonsense, and she is one of the few individuals that Takao finds difficult to deal with. However, beneath this firm exterior lies a deep, genuine care and unwavering support for Takao. Mazuru's role in the story is that of a grounding force and a foil to Takao's impulsiveness, often intervening to keep her sister's antics from causing too much trouble for the hospital and its staff. In terms of background, she was an accomplished athlete in her youth, having been the star pitcher and cleanup hitter for her softball team from middle school through college, which hints at her disciplined and competitive nature. Her primary motivation is to maintain order within the hospital while protecting and guiding her sister. Though she is a supporting character, her presence is crucial for balancing the narrative and providing a pragmatic counterpoint to Takao's unrestrained curiosity.