Mizuno Ami is also known as Sailor Mercury. Her name means "Beauty of the Waters" which describes the element her powers derive from, water. Her parents are divorced and she lives with her mom in a mansion in Minato-Ku. Her father, who is a painter sends her paintings instead of letters. When Ami first appeared in Bishoujo Senshi Sailor Moon, she was at the age of 14 in her second year (class 5) of junior high school at Juuban J.H. and ends up going through 5 seasons of Sailor Moon to the age of seventeen at Juuban High. She is a very intelligent girl with an IQ of 300 and she studies very hard with hopes of following her mother's foot-steps to be a doctor and she arrives at school fourty minutes earlier to study. As a result of this, she is usually the top scorer in Japan in examinations. Because she pre-occupied with studying, Ami has a lack of social experience and this results in her saying the wrong words at the wrong time.

She is the person that understands Usagi the most and is the most patient and sensitive when it comes to Usagi's little tantrums. She is also the most mature among the Inner Senshi, always keeping a neutral stance everytime Usagi and Rei fight and usually being the one to break off the fight. The person whom she has feelings for, Urawa Ryo is one of the nijizuishou (rainbow crystal) carriers who has the ability to see into the future. Although during the only two episodes in the entire Sailor Moon series, both of them displayed mutual attraction, due to the short duration of his appearence, their relationship doesn't seem to go very far and doesn't appear to be well-established.