Yayoi Yukino, originally called La Andromeda Promethium, is the Millennial Queen dispatched from the planet La Metal to oversee Earth before its scheduled destruction. As an operative loyal to her homeworld's ruler, Holy Queen Larela, she initially supports the plan to enslave humanity prior to La Metal's collision with Earth on September 9, 1999. On Earth, she lives under the identity of Yayoi Yukino, working as a private secretary for astronomer Professor Amamori and teaching at a school. She resides in a high-class apartment. Physically, she embodies Leiji Matsumoto's signature design: a tall, willowy figure with long blonde hair, glittering eyes, and distinctly almond-shaped eyes as noted in the film adaptation. Her loyalty to La Metal wavers as she forms deep connections with humans, especially Professor Amamori and his nephew Hajime. These bonds foster compassion and attachment to Earth, leading her to reject Larela's genocidal plan. This conflict culminates in Yayoi directly challenging Larela, accepting a duel at Black Venus to decide Earth's fate. She defeats Larela but spares her life, asserting her authority as Millennial Queen to forge a new path. As La Metal approaches Earth, she coordinates protective measures for humanity, including the Noah protocol—hollow vessels designed to shield populations from planetary disasters. She remains on Earth during the climactic battle to confront Larela's forces directly, utilizing stored psychic powers inherited from previous Millennial Queens to mitigate catastrophes. The conflict results in significant losses, including allies like Yorumori and Selenium. Following the ceasefire, she identifies a destabilizing black hole affecting La Metal's orbit. To ensure long-term stability for both worlds, she departs Earth, tearfully bidding farewell to her adoptive family, Professor Amamori, and Hajime. Aboard the ship Carmilla, she collaborates with Larela to seal the black hole, redirecting La Metal's trajectory and enabling its survival. This act solidifies her role as La Metal's new ruler, where she initiates projects like an artificial sun to improve living conditions. Her reign is peaceful and prolonged. As a La Metalian, she possesses extended longevity and enhanced physical resilience, including rapid healing capabilities. Her crown grants access to psychic abilities such as psychokinesis—demonstrated when halting a tsunami—and clairvoyance, though the latter causes her physical strain. These powers derive from the collective memories and energies of prior Millennial Queens.