Ami Mizuno / Sailor Mercury

In her civilian life Ami is a teenager with a short dark blue crop that grazes her neck and blue eyes, sometimes seen behind reading glasses. Day to day she wears the Juban Public Middle School uniform, cycling through summer and winter casual sets over the seasons and moving up to the Juban High School uniform once Sailor Stars begins.

Her Sailor Mercury outfit is a white armored leotard trimmed with a blue collar, choker, and skirt plus paired light blue bows, worn with blue heeled boots, elbow-length gloves, and a gold tiara holding an oval blue gem. A press of one earring summons her Mercury goggles for battlefield readouts. The Super Sailor Mercury upgrade swaps in a heart-shaped chest gem, a single collar stripe, a starred choker, and larger, partly translucent shoulder pads.

Before Usagi drew her out, Ami kept to herself, filling her hours with books and study and rarely making friends. Because she topped national exams by seemingly superhuman margins, classmates dismissed her as stuck-up, an impression that softened once the two girls grew close.

At heart she is gentle, kind, loyal, and a little insecure, leaning early on what her mother and teachers think before settling into her own confidence. She becomes the group's strategist, reading enemies and anticipating their moves, and as the most level-headed Inner Guardian she detests conflict, especially the constant bickering between Usagi and Rei. Her parents are divorced and her hardworking mother is often away, so she looks after herself while chasing a dream of practicing medicine. Math and science are her favorites, though she quietly loves romance novels and pop culture.

Mercury debuts in the eighth episode of the original series. After she again ranks first in the country, Luna suspects the strange aura around her belongs to the enemy, but Usagi's friendship and a record round of the Sailor V game suggest otherwise. A brainwashing study disk leads Luna back to her, and when the monster Garoben tries to drain her genius, Ami refuses to cheat her way to grades, the mark of Mercury flares on her brow, and she transforms to fog the creature with Bubble Spray. She later grows close to Ryo Urawa, then gives her life beside the others against the DD Girls, before the whole team loses their memories when the Dark Kingdom falls.

Across Sailor Moon R she returns to duty, first facing the Cardians of the Makai Tree and then the Black Moon Clan, where her rival Berthier of the Spectre Sisters bends ice against her and traps her in a rigged chess match. Her answers here run from Bubble Spray Freezing to Shine Aqua Illusion, and she briefly weighs leaving for medical study in Germany before choosing to stay. In the S season she races Michiru in the pool, loses her Pure Heart Crystal to a Daimon, and lends her power to Super Sailor Moon during the war with the Death Busters.

Her arc in Sailor Stars centers on the Starlights, above all Taiki, who dismisses love and friendship as lesser things than science. In one of her strongest moments of the season, Ami gradually shifts his thinking, and Taiki grows closer to her than to any other Guardian. Through all of it she remains the mind of the team, backed by her Mercury Visor and a compact supercomputer that crack any problem set before her.