Maomao is the central protagonist of The Apothecary Diaries, a young woman with an extraordinary knowledge of medicine, herbs, and toxins. Her background is marked by hardship and unconventional upbringing. She is the illegitimate daughter of the La Clan, a prestigious military family, but was raised in the red-light district by her adoptive father, Luomen, a brilliant physician who served as her mentor. This formative environment, combined with Luomen's rigorous instruction, gave her a comprehensive and practical education in pharmaceuticals, diseases, and human physiology that is highly unusual for a girl of her social standing. Her early life was defined by poverty and the harsh realities of the pleasure quarter, which instilled in her a deeply pragmatic worldview. Her life took a drastic turn when she was kidnapped by bandits and sold to the Imperial Palace as a low-ranking servant. Initially intending to serve out her two-year indenture quietly, her keen observations and encyclopedic knowledge soon drew the attention of the powerful eunuch Jinshi after she anonymously solved a mystery involving poisoned cosmetics that were sickening the emperor's consorts and children.

Maomao's personality is defined by a dry, deadpan demeanor, a sharp intellect, and a relentless, scientific curiosity. She is highly practical, resourceful, and observant, always prioritizing survival and the acquisition of knowledge. She possesses a sarcastic wit and a deadpan expression that rarely betrays her inner thoughts. A defining trait is her insatiable thirst for understanding chemical and biological processes; she is genuinely fascinated by poisons, medicines, and the mechanics of disease, often testing compounds on herself to build immunity or verify their effects. She is also notably reserved and prefers to avoid attention, acutely aware of her low status and the dangerous dynamics of palace life. Despite this, she harbors a strong, private sense of justice and empathy, which often compels her to intervene when she sees harm being done, even when it puts her at risk. She is one of the very few people in the palace who is completely unaffected by Jinshi's extraordinary beauty, a fact that is a source of both humor and narrative tension.

Her primary motivation is intellectual rather than ambitious. She is driven by an intrinsic need to solve puzzles and understand the world through a chemical and logical lens. She does not seek power, status, or wealth; instead, she views her circumstances as opportunities for observation and research. When she solves mysteries, it is almost always because her curiosity is piqued or because she feels a moral obligation to act, not for personal gain. Her ultimate goal is to return to a quiet life of apothecary work, though her growing involvement in palace intrigue continually delays this.

Within the story, Maomao's role evolves from a humble servant and poison taster for the consort Gyokuyou into an unofficial forensic pathologist, detective, and trusted medical advisor to the royal court. She becomes the linchpin of the palace's medical system, handling diagnoses and procedures that even male physicians struggle with, and she is the key investigator of numerous complex plots, illnesses, and deaths. Her perspective is the central lens through which the audience experiences the world of the Imperial Palace.

Her most significant relationship is with Jinshi, the enigmatic and beautiful eunuch who initially recruits her services. Their dynamic is a slow-burn puzzle in itself; Maomao views him with clinical detachment and professional annoyance, while Jinshi is deeply intrigued by her immunity to his charm and her unparalleled competence. Their relationship is built on mutual respect for each other's abilities, and it gradually develops into a deeper, subtle bond. Another key relationship is with her adoptive father, Luomen, who is her only genuine emotional anchor and the source of all her medical knowledge. She also forms a protective and respectful bond with the consort Gyokuyou, who becomes an early supporter and friend. Later, she interacts with her biological father, the strategic military official Lakan, in a complex game of wits that carries emotional weight from her past.

Maomao undergoes subtle but meaningful development throughout the series. Initially closed-off and averse to emotional attachments, she gradually opens up, learning to navigate complex social relationships and beginning to acknowledge her own feelings, particularly regarding Jinshi. Her arc involves learning to balance her detached, analytical nature with a growing capacity for personal connection and empathy, and she slowly confronts her own trauma and past. She remains intellectually driven, but her emotional world expands.

Her most notable abilities are her encyclopedic knowledge of medicinal herbs, poisons, and basic chemistry, her exceptional powers of deductive reasoning and observation, and her practical experience in diagnosis and treatment. She has a highly developed resistance to many poisons from years of self-experimentation, she possesses a remarkable memory for symptoms and compounds, and she is highly skilled at reading people and situations, which allows her to navigate the treacherous social landscape of the palace with silent diplomacy.