*One day in Juban, Tokyo, a middle-school student named Usagi Tsukino befriends Luna, a talking black cat who gives her a magical brooch enabling her to transform into Sailor Moon: a guardian destined to save Earth from the forces of evil. Luna and Usagi assemble a team of fellow Sailor Guardians to find their princess and the Silver Crystal.

They encounter the studious Ami Mizuno, who awakens as Sailor Mercury; Rei Hino, a local Shinto shrine maiden who awakens as Sailor Mars; Makoto Kino, a tall and strong transfer student who awakens as Sailor Jupiter; and Minako Aino, a young aspiring idol who had awakened as Sailor Venus a few months prior, accompanied by her talking feline companion Artemis. Additionally, they befriend Mamoru Chiba, a high school student who assists them on occasion as Tuxedo Mask.

In the first arc, the group battles the Dark Kingdom, those members attempt to find the Silver Crystal and free an imprisoned, evil entity called Queen Metaria. Usagi and her team discover that in their previous lives, they were members of the ancient Moon Kingdom in a period of time called the Silver Millennium. The Dark Kingdom waged war against them, destroying the Moon Kingdom.

Its ruler Queen Serenity sent her daughter Princess Serenity, reincarnated as Usagi, along with her protectors the Sailor Guardians, their feline advisers Luna and Artemis, and the princess's true love Prince Endymion, who in turn was reborn as Mamoru.

At the beginning of the second arc, the Sailor Guardians meet Usagi and Mamoru's future daughter Chibiusa, who arrives from a 30th-century version of Tokyo known as "Crystal Tokyo", which is ruled by Neo Queen Serenity, Usagi of the future and has been attacked by the group of villains known as the Black Moon Clan. During their journey, Sailor Moon and her friends meet Sailor Pluto, Guardian of the Time-Space Door.

During the climactic battle of the arc, Sailor Pluto dies trying to save the sailor soldiers and Chibiusa was brainwashed by the enemy and turned into the Black Lady.*