Once upon a time... exactly one thousand years ago, all the planets were at peace. This period of time was called the Silver Millenium, and it was a happy and prosperous time for human kind. The universe was ruled by Queen Serenity, a beautiful and just Queen, who lived on the Moon with her daughter Princess Serena. Queen Serenity was raising her daughter to follow her footsteps and be the future Queen of the Moon. The Moon Kingdom led all the planets during the Silver Millenium.

However, on the other side of the Universe, a threat to this long-lasting peace existed in the form of the Negaverse. The Negaverse Kingdom was the direct opposite of the Moon Kingdom. It was a place of hatred, deceit, cruelty, torment, and evil. At the core of the Negaverse, an entity existed which was the main force in the Negaverse, called "The Negaforce". The Negaverse itself was ruled by an evil woman, Queen Beryl. With the help of the Negaforce, Beryl planned to conquer the Universe, starting with the Moon.

Meanwhile, Princess Serena had fallen in love with a prince from Earth, Prince Darien. They were deeply in love and had plans for marriage. One night Prince Darien came to visit Serena with bad news... he told her Queen Beryl was planning on attacking the Moon and that he was going to fight against them on war to defend the Moon. Serena gave Darien her star locket so he would never forget her. Princess Serena and Darien met again later that night at a Masquarade ball, which was going to be the last one on the Moon Kingdom... During a lunar eclipse, Queen Beryl led her army to the moon, and quickly began their attack. Four young girls, the princesses of their respected planets, attempted to fight off the Negaforce, but the Moon Kingdom warriors were no match for the overwhelming, relentless forces of the Negaverse. Prince Darien fought bravely against the Negaforce defending Serena, but Queen Beryl succeeded in defeating the Moon Kingdom and killing everyone, including Queen Serenity's only daughter Serena and her only and true love Prince Darien.

After the decisive battle, the Negaverse claimed victory. Queen Serenity knew that she could not let the Negaverse win. She resorted to one final act. Using the power of her Imperium Silver Crystal, Queen Serenity purged the universe of its invaders. Queen Beryl, the Negaforce, and Negavere's army were all sent back to the Negaverse. Also she sent many of her people away, so that they may live in peace once again.

Her daughter, along with her court of princesses and their two guardian cats, was sent one thousand years into the future, to our present-day earth. Queen Serenity wasn't going to let Beryl stand on the way of her daughter's happiness, so she gave Serena life, so that her people and her universe could live in peace once more. She knew her daughter had to go on, because she was destined to be the next Queen of the Universe. Serenity was sad because she knew that on earth her daughter and friends were not going to remember their lives on the Moon. But she had hopes to reunite with her daughter somehow, someday.... Luna and Artemis, the cats, were sent as advisors. If Queen Beryl tried to break into our universe again, Luna and Artemis would find and alert the Sailor Scouts to fight off any new threats from the evil Megaforce. Queen Beryl had sworn that she would conquer the universe, and one thousand years after the destruction of the Moon Kingdom, she had her chance once again.