The protagonist of Sailor Moon, Usagi Tsukino, an ordinary ditsy middle-school girl - or so she herself thinks, at least - discovers a talking cat named Luna, who reveals Usagi's identity as "Sailor Moon," a special warrior with the destiny of saving the planet Earth, and later the entire galaxy. Usagi, who is the reincarnation of the Moon Princess, must now protect Earth from a series of villains, beginning with the Dark Kingdom that had appeared once before, long ago, and destroyed the kingdom of the moon.The characters in Sailor Moon awaken members of the court of the kingdom of the moon, and the people dedicated to protecting it; when the dark nemesis attacked the kingdom, the Queen sent the Moon Princess, her guardians and advisors, and her true love into the future to be reborn. As Usagi and Luna battle evil and search for the Moon Princess, they meet the other Sailor Senshi, incarnations of the Moon Princess' protectors, and the mysterious Tuxedo Mask.
As the series progresses, Usagi and her friends learn more and more about the enemies they face and the evil force that directs them. The characters' pasts are mysterious and hidden even to them, and much of the early series is devoted to discovering their true identities and pasts. Luna, who teaches and guides the Sailor Senshi, doesn't know everything about their histories either, and the Senshi eventually learn that Usagi is the real Moon Princess. The Moon Princess' mother had her reborn as a Sailor Senshi to protect her. Gradually Usagi discovers the truth about her own past life, her destined true love, and the possibilities for the future of the Solar System.
The plot spans five major story arcs, each of them represented in both the manga and anime, usually under different names:
1.the Dark Kingdom arc (Sailor Moon)
2.the Black Moon arc (Sailor Moon R)
3.the Death Busters arc (Sailor Moon S)
4.the Dead Moon arc (Sailor Moon SuperS)
5.the Shadow Galactica arc (Sailor Moon Sailor Stars)
The anime added an additional minor arc at the start of the second series, and spent the first few episodes of Sailor Stars wrapping up the plot from the previous series. Taking place before the manga timeline, its sister series Codename: Sailor V tells the story of Sailor V, Minako Aino and her adventures during the year before Sailor Moon itself starts. Many characters from Codename: Sailor V return in Sailor Moon, including Sailor V herself (under the name "Sailor Venus").