Kakyuu is the princess of the SailorStarlights. The Starlights come to Earth in search of her.
Princess Kakyuu makes her first actual appearance in episode 193, floating in the air and holding Usagi in her arms. Usagi and ChibiChibi were sucked into a black hole that Tin Nyanko created, and ChibiChibi called Kakyuu using her Chalice, where Kakyuu had hidden herself. In episode 194, her identity as the Starlights' princess is revealed. ChibiChibi is the one who helped Kakyuu find Earth, using the chalice and caring for it. After arriving, Kakyuu asks the Sailor Senshi to help her stop Galaxia, but Uranus and Neptune are angered by her request so Kakyuu leaves with the Starlights.
In episode 195, her star seed is taken by Galaxia, and she subsequently dies. However, she comes back to life at the end of episode 200 after Galaxia is healed by Sailormoon. Then Kakyuu and the Starlights leave Earth to start a new life.