Usagi Tsukino was a normal second-year middle school girl whose own life changes one day when she encounters a black cat. The cat's name is Luna who can talk and bears a cresent moon on her forehead. Luna tells Usagi that she is the chosen guardian of justice with the power to transform into Sailor Moon. Usagi now has a new responsiblity which is a mission to find the Illusionary Silver Crystal as well as the other chosen guardians to protect the Moon Princess. During her mission, she must deal with various enemies sent by Queen Beryl who is also after the Illusionary Silver Crystal.

Just when Usagi Tsukino thought life would be back to normal a little girl literally falls out of the sky. The girl has a striking resemblance to Usagi and even shares the same name as her. Turns out Chibiusa is from the future and she is on a mission to find the Silver Crystal that could help save her timeline from an evil threat. However she is being hunted by members of the Dark Moon Clan who were behind attacking her home world. It is up to Sailor Moon and the Sailor Guardians to help protect Chibiusa and save the future. Usagi thinks life may be back to normal when a little girl literally falls out of the sky. She also calls herself Usagi and she seeks the help of Sailor Moon and the Sailor Guardians to help her save the future. When the Dark Moon attacks modern-time Japan, it looks like the threats of the future are also out to destroy the past.

The third season will focus on the Death Busters arc (also called the Infinity arc), adapting the arc from the fifth and sixth volumes of the complete edition of Naoko Takeuchi's original Sailor Moon manga.