The love between Serena and Darien first began on the Moon Kingdom in their past lives. As Princess Serenity she was the crown princess of the Silver Millennium, but she showed little interest in her royal duties as she was infatuated with Prince Endymion of the Earth Kingdom. Contact between the two kingdoms was permanently forbidden for unknown reasons. However, the Princess would often travel to Earth to be in Endymion's arms. When Queen Beryl killed Endymion in front of the Princess' eyes during her invasion of the Silver Millennium, Serenity took her own life with his sword. In the present day they met on the streets when Serena through a paper with a bad grade behind her and it hit Darien in the head (though technically they met once before when they were both very young fo a brief moment in a hospital). They re-met again as Sailor Moon and Tuxedo Mask, though it wasn't until queen Beryl had brainwashed him and Sailor Moon saved him and then he protected Sailor Moon from Queen Beryl that their memories from the Moon Kingdom returned to them. Once their memories returned they were in love again. In the future they marry and have a daughter together named Rini.