In Sailor Moon, Usagi meets Luna, a cat-like creature that is searching for the Moon Princess. Luna discovers that Usagi is destined to save Earth from the forces of evil and gives her a brooch to transform into Sailor Moon. She asks Usagi to form the Sailor Soldiers, find their princess and protect the "Legendary Silver Crystal". As Usagi matures, she becomes a powerful warrior and protects her adopted home planet, Earth, from villains who wish to harm it. Usagi is depicted as carefree and cheerful when at ease but promptly serious and strategic-minded when fighting.

As the protagonist, Usagi appears in every episode, film, television special, and original video animation (OVA) of the anime adaptations, Sailor Moon and Sailor Moon Crystal; as well as the live action adaptation, Pretty Guardian Sailor Moon. She also cameos in the sister series Codename: Sailor V. She has been the subject of parodies and has appeared in special events. Most Western audiences were introduced to Usagi appearing in the Sailor Moon anime, which is an adaptation of the manga series. Usagi's critical reception has been largely positive and she is recognized as one of the most important and popular female  superheroes of all time.