"Queen Millennia" is a science fiction anime series based on the manga by Leiji Matsumoto. The narrative centers on the conflict between Earth and the mysterious planet La Metal, which orbits the solar system every millennium. La Metal is ruled by Queen La Andromeda Promethium, also known as Queen Millennia, who seeks to conquer Earth to ensure the survival of her own civilization. The story begins with the discovery of La Metal's impending approach, which threatens Earth with catastrophic consequences.

The protagonist, Hajime Sakomizu, is a young astronomer who becomes entangled in the unfolding events. Hajime's life takes a dramatic turn when he encounters Yayoi Yukino, a mysterious and intelligent woman who is revealed to be Queen Millennia herself. Yayoi has been living on Earth in disguise, gathering information and preparing for La Metal's arrival. However, her time on Earth has led her to develop a deep affection for humanity, creating an internal conflict between her duty to her people and her growing empathy for Earth's inhabitants.

As the story progresses, the tension between Earth and La Metal escalates. Queen Millennia's forces, including her loyal subordinates, initiate plans to subjugate Earth, while Earth's scientists and governments scramble to understand and counter the threat. Hajime, along with his friends and allies, becomes a key figure in resisting La Metal's invasion. The narrative explores themes of loyalty, sacrifice, and the moral complexities of survival, as characters on both sides grapple with their roles in the impending conflict.

The series delves into the backstory of Queen Millennia, revealing her tragic past and the burdens of leadership. Her relationship with Hajime becomes a focal point, as their bond symbolizes the potential for understanding and coexistence between the two worlds. The plot builds toward a climactic confrontation, where the fate of both Earth and La Metal hangs in the balance. The resolution emphasizes the possibility of reconciliation and the enduring hope for peace, even in the face of seemingly insurmountable differences.