A chance encounter with a plush toy cat that falls from the sky forever changes the life of the ordinary and slightly clumsy middle school student Usagi Tsukino. The cat, who introduces herself as Luna, reveals that Usagi is no ordinary girl but a reincarnated warrior destined to protect the Earth. Gifted with a special brooch, Usagi transforms into Sailor Moon, a guardian in a sailor-style uniform who fights the evil forces of the Dark Kingdom. Her mission is to find the legendary Moon Princess and the mystical Silver Crystal, a powerful artifact sought by the villains to plunge the world into darkness.

Set in modern-day Tokyo, the series unfolds as Usagi is not alone in her duty. She is gradually joined by four other heroines: the brilliant and soft-spoken Ami Mizuno, who becomes the logical Sailor Mercury; the powerful shrine priestess with a fiery temper, Rei Hino, who becomes Sailor Mars; the gentle yet strong transfer student Makoto Kino, who becomes Sailor Jupiter; and the famous and popular pop idol Minako Aino, who is already active as the crime-fighting Sailor Venus. They are often aided by a mysterious masked figure, Tuxedo Mask, the alter ego of a college student named Mamoru Chiba, whose own past is deeply intertwined with the destiny of the Sailor Guardians.

The 49-episode series introduces several unique twists to the classic story. Unlike other versions, Luna is an immobile plush doll that can talk, while the girls' hair only changes color when they transform. Their civilian lives are heavily featured, including the transformation of the Game Center Crown into a karaoke box where the friends often gather. The personal struggles of the heroes are given more weight, such as Minako secretly suffering from a serious illness while maintaining her idol career. This iteration also features original characters not found in the source material, including Hina Kusaka, Mamoru's arranged fiancée who complicates his relationship with Usagi, and Mio Kuroki, a young idol who secretly serves as the shadow of the primary villain, Queen Beryl.

As the narrative progresses towards its climax, it diverges significantly into darker and more dramatic territory. Ami is temporarily brainwashed by the enemy, transforming into the formidable Dark Mercury and forcing the Guardians to fight their friend. The internal conflict reaches a peak when Usagi discovers that she is the very Moon Princess she was searching for, causing a rift in her personality as the ancient spirit of Princess Serenity battles for control within her. The stakes become intensely personal, leading to the tragic death of Sailor Venus before the final battle. Ultimately, the Sailor Guardians must confront Queen Beryl and the malevolent entity Queen Metalia, culminating in a conclusion where the surviving warriors lose their powers and memories, finally free to live ordinary lives until fate offers them a final chance to reunite.