Ami Mizuno is a fourteen-year-old student at Juban Public Middle School, renowned for exceptional academic performance including top national exam scores and a rumored IQ of 300. Her intellectual focus initially isolates her, as peers misinterpret her shyness as aloofness. She lives with her mother, Dr. Saeko Mizuno, a physician she aspires to emulate, while her father, a painter, lives separately after their divorce, maintaining limited contact through annual birthday cards—a familial dynamic contributing to her early loneliness. In her civilian identity, she exhibits keen analytical abilities, excelling in mathematics, science, and computer technology. She demonstrates proficiency in chess and competitive swimming, alongside unexpected skill in arcade gaming. Outside academics, she enjoys reading, particularly romance novels, though she conceals this interest initially. She displays hypersensitivity to romantic attention, experiencing physical allergic reactions to love letters. As Sailor Mercury, she transforms using the phrases "Mercury Power, Make Up," "Mercury Star Power, Make Up," and "Mercury Crystal Power, Make Up," wielding powers derived from the planet Mercury. Her abilities center on hydrokinesis, cryokinesis, and atmidokinesis, enabling manipulation of water in all states: liquid, ice, snow, mist, and steam. Initial techniques prioritize tactical support, such as Mercury Aqua Mist for battlefield obscuration and intelligence gathering via summoned visor goggles that analyze enemy vulnerabilities. A communicative earring microphone facilitates team coordination. Her character evolves through key conflicts: during the Dark Kingdom arc, brainwashing at the Crystal Seminar is overcome when Usagi's peril triggers her awakening as Sailor Mercury. In the Black Moon arc, she demonstrates extrasensory hydrokinetic perception to locate pipe malfunctions while civilian. Her strategic intellect is tested against Berthier in a high-stakes chess match where emotional resilience proves vital after psychological manipulation targeting her parental abandonment. The Infinity arc introduces Mercury Aqua Mirage, an offensive water-spiral attack, alongside enhanced analytical applications of her goggles against Daimon enemies. Transformational evolutions reflect power progression: her base Crystal uniform features a sleeveless blue design with three-striped collar, circular chest brooch, and asymmetrical ear studs (three left, one right). Ascension to Super Sailor Mercury reduces collar stripes to one, adds translucent shoulder pads, replaces the brooch with a heart shape, and incorporates a star-adorned choker. The Eternal Sailor Mercury form alters the costume with a V-shaped choker, layered skirt, star-shaped chest brooch, elongated gloves with vambraces, and knee-high boots featuring star accents. Interpersonal relationships define her growth: Usagi's persistent friendship breaks her isolation, fostering gradual confidence. Team dynamics position her as primary strategist, utilizing computational devices for tactical analysis during combat. While romantic subplots remain undeveloped in Crystal, her loyalty manifests protectively, notably persuading Outer Guardians against lethal force toward Hotaru. Familial reconciliation occurs when she asserts autonomy, rejecting her mother's attempted school transfer by prioritizing current responsibilities over academic demands. Alternative media portrayals include musical explorations of her conflict between studying abroad and guardian duties, while the live-action series introduces "Dark Mercury" under Kunzite's brainwashing. The "Parallel Sailor Moon" narrative depicts a future where she becomes a physician, marries, and mothers a daughter named Ami Jr. who also becomes a Sailor Guardian.