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 soldier destined to save Earth from the forces of evil. Luna and Usagi assemble a team of fellow Sailor Soldiers 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. Led by Queen Beryl, a team of generals—the Four Kings of Heaven (四天王, Shiten'ō, lit. "Four Heavenly Kings")—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, resulting in the destruction of the Moon Kingdom. Its ruler Queen Serenity later sent her daughter Princess Serenity, her protectors the Sailor Soldiers, their feline advisers Luna and Artemis, and the princess' true love Prince Endymion into the future to be reborn through the power of the Silver Crystal. The team recognizes Usagi as the reincarnated Serenity and Mamoru as Endymion. The Soldiers kill the Four Kings, who turn out to have been Endymion's guardians who defected in their past lives. In a final confrontation with the Dark Kingdom, Minako kills Queen Beryl; she and the other Soldiers then sacrifice their lives in an attempt to destroy Queen Metaria. Using the Silver Crystal, Usagi defeats Metaria and resurrects her friends.
At the beginning of the second arc, Usagi and Mamoru's daughter Chibiusa arrives from the future to find the Silver Crystal. As a result, the Soldiers encounter Wiseman and his Black Moon Clan, who are pursuing her. Chibiusa takes the Soldiers to the future city Crystal Tokyo, where her parents rule as Neo-Queen Serenity and King Endymion. During their journey, they meet Sailor Pluto, guardian of the Time-Space Door. Pluto stops the Clan's ruler Prince Demand from destroying the spacetime continuum, leading to her death. Chibiusa later awakens as a Soldier—Sailor Chibi Moon and helps Usagi kill Wiseman's true form, Death Phantom.