TV-Series
Description
Ami Mizuno is a teenage schoolgirl who resides in the Azabu-Juban district of Tokyo and is a central member of the Sailor Guardians. She lives with her mother, Dr. Saeko Mizuno, a busy and respected physician whose demanding career keeps her away from home frequently. Her father, a painter, lives separately from the family following their divorce and maintains only limited contact with Ami, typically sending her postcards or paintings on her birthday. This family dynamic contributes to a sense of loneliness and self-reliance in her early life. Ami is an only child who dreams of following in her mother's footsteps to become a doctor.

Her most defining characteristic is her extraordinary intelligence, with a rumored IQ of three hundred, which consistently places her at the top of national academic rankings. She has a particular aptitude for mathematics and science and is a member of her school's computer club. Her peers often misinterpret her inherent shyness and studious nature as aloofness or snobbishness, leading to a degree of social isolation before she befriends the other Guardians. Despite her academic focus, Ami has a hidden appreciation for pop culture and enjoys reading romance novels, though she is usually embarrassed to admit to these interests. Her hobbies include playing chess and swimming, which she uses as a method to relax. She has an unusual physical allergy to love letters, which causes her to break out in a rash.

Throughout the series, Ami is portrayed as kind, gentle, and deeply loyal, with a strong aversion to unnecessary conflict and a dislike of quarreling, particularly between her more hot-headed teammates. She is the most sensible and level-headed member of the group, often serving as the voice of reason and the one who is most embarrassed by their collective silliness. Initially insecure and heavily reliant on the approval of her mother and teachers, she grows significantly more confident and assertive as the story progresses. Her unwavering loyalty to her leader, Sailor Moon, is a central part of her character, and she is repeatedly shown to be willing to sacrifice her own life to protect her princess and friends.

As the second Guardian to be discovered by Sailor Moon, Ami transforms into Sailor Mercury, the Guardian of Water and Wisdom. Her powers are derived from the planet Mercury, and in keeping with the Japanese name for the planet, Suisei, which contains the character for water, her abilities are primarily water and ice-based. Her role within the team is that of the strategist and tactical analyst. In battle, she uses a unique handheld computer and a visor that she can summon to analyze enemy weaknesses, gather information, and coordinate attacks. Her early abilities are more supportive than offensive, such as Shabon Spray or Mercury Aqua Mist, which creates a thick fog to obscure the enemy's vision and allow the team to regroup or launch a surprise attack. As she grows stronger, she gains more potent offensive techniques, including Shine Aqua Illusion, which unleashes a powerful wave of water that can also freeze targets, and later, Mercury Aqua Rhapsody, performed with the Mercury Harp.

Her key relationships are central to her development. Her friendship with the protagonist, Usagi Tsukino, is transformative; Usagi is the first person to see past Ami's shy exterior and recognize her kindness, drawing her out of her shell and into the circle of friends she never had. She shares a close bond with the other Inner Guardians, often acting as a mediator, particularly between Usagi and Rei Hino. A significant moment in her personal development involves a decision to turn down an opportunity to study abroad in Germany, choosing instead to remain in Japan to fulfill her duties as a Guardian and stay with her friends, reaffirming her commitment to her new life and purpose.

Over the course of the narrative, Ami's power and uniform evolve to reflect her growth. She achieves a more powerful form known as Super Sailor Mercury after obtaining the Mercury Crystal, and later attains an Eternal Sailor Mercury form. Her aspiration to become a doctor is a recurring theme that creates internal conflict between her academic ambitions and her responsibilities as a Guardian, a tension she ultimately resolves by integrating her intellect and compassion into her heroic role. In the live-action adaptation, she is temporarily brainwashed by the Dark Kingdom to become Dark Mercury, a stark contrast to her usual gentle nature. In the far future of Crystal Tokyo, she serves as a trusted guardian to the royal family.