Ami's most-emphasized character trait is that she is enormously intelligent—in the anime and manga she is rumored by other characters to have an IQ of three hundred, while in the stage musicals this is stated as a fact. She is adept at English in both the musicals and the anime. Her peers view her with a mixture of awe and distaste, misinterpreting her inherent shyness as snobbery, and so she tends to have a difficult time making new friends. Ami is depicted as sweet, gentle, and loyal, as well as slightly insecure. Anne Allison describes her as "a smart girl who needs to relax", calling her "conscientious" and "studious", "everything Usagi is not". Early on in the story, she relies heavily on the approval of her mother, teachers, and friends, but as the series progresses she becomes stronger and more confident in herself. She is generally the most sensible of the main characters, and is often the only one embarrassed when the group has a dull-witted moment. As the story begins, she attends Azabu Jūban Junior High along with Usagi Tsukino and, later, Makoto Kino.
Throughout the series, much of Ami's free time is spent studying. She loves to read, and dreams aloud of one day being a doctor like her mother and becomes one in both Parallel Sailor Moon and the live action series. In the musicals, Ami's dream of being a doctor and leaving Japan to study abroad is a recurring theme. The first part of the song Dream Yume wa Ookiku shows Ami's conflict between studying abroad and growing up or being with everyone else and staying a young girl. She faces a similar dilemma in the anime, but very directly; given the opportunity to study in Germany, she gets as far as the airport before deciding to stay in Japan and fight evil alongside her friends.
Ami has great appreciation for art as well as science, and, contrary to the usual depiction of a bookworm, even enjoys pop culture and romance novels (though she is usually embarrassed to admit it). In both the anime and the manga, Ami's diligence in her studies becomes a running gag; she often comically scolds Usagi and the others for not doing their homework, and she can become obsessive about being the best student. Her character has been interpreted as a political commentary on the education system of Japan. She sometimes displays attraction to boys her age, and other times aversion to the idea. Love letters are listed as the one thing she has most trouble with, and when she later receives one, it gives her a rash. In the anime, a classmate named Urawa learns her identity and expresses attraction to her, but this is never resolved, as he disappears after just two appearances in the first series.
Besides reading, Ami is shown playing chess and swimming in order to relax. As the team scholar, computers are listed her strong point; she even belongs to the club at school. She loves all her classes, especially mathematics. Her favorite foods are given as sandwiches and anmitsu, with her least favorite being yellowtail. Other loves include cats and the color aquamarine.
Ami is one of the few girls in the series whose family situation is explicitly mentioned in the anime. Her parents are divorced, and she lives with her mother, a busy doctor who is not home very often, named Saeko in the live-action series. They look very similar, and Ami admires her mother and longs to live up to her example. Besides her workaholic tendencies, Ms. Mizuno is portrayed as a good person who openly resents not having more time to spend with her daughter. Ami's father is never named, but is stated in the manga and anime to be a painter. The manga says that he never visits them, having decided one day not to come home from the forest where he was relaxing and painting, but he sends her postcards on her birthday. Thinking about this, Ami sometimes resents her parents' selfishness in separating, partly because divorce in Japan is taboo. However, in the anime Ami seems to appreciate her father and seems to share some of his artistic traits, at one point even composing matching lyrics for a tune that had none. In the manga, Ami's mother is revealed to be fairly rich, as they live in a condominium. Ami is shown testing the strength of a sword that the Sailor Senshi received on the moon by using it to chip a diamond ring. (Classically, a diamond is the hardest mineral.) When the girls panic, she calms them by saying that her mother has many more.
In the live-action series, Ami is especially shy and usually wears glasses while in public, even though she does not need them. At her middle school, she has no friends before meeting Usagi and always eats lunch alone on the roof so she can study. Usagi seems to be the only one to realize that Ami is merely shy, not truly standoffish, and in befriending her gradually helps Ami to learn that she is more than just a bookworm. By Act 34, when Ami's mother attempts to transfer her to another school because she thinks Ami's friends are bad influences, Ami rebels, avoiding the admission interview and spending the night at the Senshi hideout with Rei Hino. Later she tells her mother that what she's doing in her life right now is more important than studying, and her mother understands.
Ami was a kind and gentle person who disliked quarrels and abhorred harming innocent people. This trait was even cited in the title of an anime episode, "Believe in Love! Ami, a Kind Hearted Senshi," where she persuaded Sailor Uranus and Sailor Neptune not to kill Hotaru. Like her comrades, her loyalty to Sailor Moon was unwavering, and she would sacrifice her life for her princess if necessary.
Special powers and items In the manga, Ami can dowse without any aids. Otherwise, she is not shown using any special powers in her civilian form, and may not be able to. She must first transform into a Sailor Senshi by raising a special device (pen, bracelet, wand, or crystal) into the air and shouting a special phrase, originally "Mercury Power, Make-up!" As she becomes more powerful and obtains new transformation devices, this phrase changes to evoke Mercury Star, Planet, or Crystal Power. In the anime, Sailor Mercury's transformation sequence evolves slightly over time, whether to update the background images or to accommodate changes to her uniform or a new transformation device, but all of them involve a stream of water which she whirls around her body as she spins, forming her outfit with a ripple effect.
Sailor Mercury has the power to manipulate water. For the entire first story arc, she uses her powers only to create dense clouds of mist, chilling and blinding the enemy while her allies prepare more direct attacks. In the manga she usually does this without speaking, while in the anime it is given the name Shabon Spray. In the updated renewal manga, this power is renamed Mercury Aqua Mist to match the live-action series, in which she has an offensive beam attack by that name, capable of destroying weaker enemies. She uses a total of five attacks in this series, most of which are variations on the first.
Sailor Mercury's first major offensive attack is Shine Aqua Illusion, introduced in the second story arc, which can be used as a simple projectile, to freeze the enemy in solid ice, or to create a defensive barrier. Aside from variations on her other powers (mostly improving their strength with the addition of "Freezing" or "Snow"), her next named attack is Mercury Aqua Mirage, used during the third arc of the manga and again in the special side-story "Ami's First Love" (manga and anime). Her final and greatest power comes in the fourth story arc, when she takes on her second Senshi form (Super Sailor Mercury in the anime). At this stage she acquires a special weapon, the Mercury Harp, and with it Mercury Aqua Rhapsody, which is her primary attack for the duration of the story. In the anime Mercury gains the harp deep within her subconcious. The manga took a different approach with the Mercury Harp making it more of an item rather than a harp formed due to the attack. Furthermore Sailor Mercury gained the harp through her power guardian. In the manga the Mercury Harp, as well as the other inner senshi's weapons have their own "wills" and can even speak and give input.
In addition to her own powers, Sailor Mercury has more non-magical items than any other Senshi. Early on in the series she makes frequent use of an extremely powerful "Micro-miniature Super Computer" that enables her to make special calculations, scan her surroundings, track the movements of allies as well as foes, and determine her enemies' weak points. The computer works in sync with her Mercury Goggles, which analyze the area around her and display information in front of her eyes and on the Computer. The visor may be a hologram of some sort; it materializes across her face when she touches her earring. The manga sometimes shows her wearing a small microphone connected to her earring, which she uses to communicate with Luna at the Senshi hideout during the manga's first arc. All of these devices gradually fall out of use as the series progresses. In the live-action series, like most of the other Senshi, she receives a tambourine-like weapon called the Sailor Star Tambo. She is one of two Senshi to use it for a named attack (Mercury Aqua Storm), and later can transform it into a sword. She also creates swords out of water, both as Sailor Mercury and as Dark Mercury.
In the manga, the Mercury Crystal and Mercury Harp are among her most significant magical possessions. The former is her Sailor Crystal and the source of all of her power, which becomes especially important in the fifth story arc. The harp's form is actually that of a lyre, a stringed instrument smaller than a harp, which according to Roman myth was invented by the god Mercury.