Kakyuu is the princess of Kinmoku, a fictional planet located outside our solar system. Known for her fragrance reminiscent of Fragrant Olive flowers, these blossoms are a recurring motif in her character design. The name of her planet, Kinmoku, is derived from the Japanese term for Fragrant Olives, "kinmokusei," with the suffix "sei" meaning "planet" or "star." Upon introducing herself, Kakyuu refers to her kingdom as Tankei, which is also a homonym for the Fragrant Olive shrub.
Kinmoku is home to the Sailor Starlights, who serve as Kakyuu's protectors and spend much of the narrative searching for her. However, the specifics of their story differ between the manga and the anime.
Before the story begins, Kinmoku is attacked and destroyed by Sailor Galaxia, leaving almost no survivors. Kakyuu travels to Earth and hides within an incense burner protected by a small child named ChibiChibi. With no contact from her, the Sailor Starlights follow her to Earth, desperately seeking her whereabouts.
In the manga, Kakyuu is injured during her battle with Galaxia and cannot reveal herself until her wounds heal. She journeys to Earth sensing the birth of the Silver Moon Crystal, an evolved form of the original Silver Crystal. She is revealed to be Sailor Kakyuu and shares with Sailor Moon that her lover died in the war against Galaxia. Eventually, she joins Sailor Moon to confront Galaxia in Zero Star Sagittarius but is killed by Sailor Chi. In her final moments, she expresses a desire to be reborn in a world without war or at least to reunite with everyone.
In the anime, there is no mention of battle injuries, and her purpose for coming to Earth is to find the "Light of Hope" and evade Galaxia. While under ChibiChibi's care, she knows the Sailor Starlights are searching for her but cannot reveal herself immediately. She eventually emerges to save Sailor Moon and others from a black hole and resumes leadership of the Starlights. Shortly after being found, Galaxia appears and takes Princess Kakyuu's star seed. Unlike in the manga, Kakyuu never transforms into a Senshi but is shown to possess a "true star seed." Before dying, Kakyuu has a vision revealing that ChibiChibi is the Light of Hope. After Sailor Moon defeats Chaos, Princess Kakyuu is revived, and she and her Starlights return to Kinmoku to rebuild and start anew.
