Mīme is a mysterious alien woman and a core member of the crew aboard the space battleship Arcadia. She is the last surviving member of her species, originating from the planet Jura, and was rescued by Captain Harlock after her home world and people were lost. In gratitude for saving her life, she pledged herself to Harlock's cause and became his closest companion, devoting her existence to his support and safety.

Physically, Mīme possesses blue skin and very long blue hair that reaches past her hips. Like others of her race, she has no visible mouth or facial features apart from almond-shaped yellow eyes. Despite lacking a mouth, she is able to communicate verbally and can absorb liquids through the general area where a mouth would be. Her biology is unusual in that she consumes alcohol as a non-intoxicating foodstuff, though consuming extremely high-proof alcohol in large amounts can induce intoxication. She also does not require sleep, which allows her to serve as a perpetual watch for the ship and its crew.

Personality wise, Mīme is quiet, brooding, and sensitive. She possesses a calm and solemn demeanor but is deeply empathetic toward those around her. Her motivations are rooted in loyalty and gratitude toward Harlock, whom she understands on a profound level. She does not seek personal glory or authority; instead, she exists to protect and aid Harlock and the Arcadia crew however she can, driven by a sense of devotion that transcends duty.

In the story, Mīme does not hold an official rank or position aboard the Arcadia, but she fulfills several vital roles. She possesses both psychic and psionic powers, which allow her to empathize with crew members in distress, sense emotions over distances, and even reduce the pain of injuries. Her empathic nature makes her a valuable counselor, and she has been known to console grieving or troubled crew members, such as when she comforted the ship's cook, Miss Masu, after a personal loss. During crises, she assists Doctor Zero in tending to the wounded. She also acts as a source of calming influence on the entire ship, able to soothe pain and anxiety by playing her lap harp.

Mīme's relationship with Captain Harlock is the most significant in her life. She is his nearest confidante and is willing to protect him at any cost. Harlock trusts her implicitly, and she often serves as a silent anchor for him amidst the chaos of their battles. Her bond with him is one of deep understanding and mutual respect, though Harlock's personal history prevents a romantic relationship from developing.

Throughout the series, Mīme's development is subtle but meaningful. She begins as a mysterious, almost ethereal figure and gradually becomes more integrated into the crew's emotional landscape, demonstrating her quiet strength and unwavering loyalty. In alternate versions of the story, her background varies; in the Harlock Saga OVA, she is reimagined as a member of the Nibelung clan and the younger sister of Alberich, defecting from her faction after witnessing her brother's evil. In this incarnation, her musical instrument becomes a pipe organ and she gains the ability to control time. However, in most canonical depictions, she retains her original Juran origin and abilities.

Notable abilities include her psychic and psionic powers, her musical talent with the harp, and her capacity for deep emotional perception. Despite her alien appearance and mysterious nature, she remains one of the most loyal and steadfast members of the Arcadia crew, embodying a quiet nobility that reflects the themes of freedom and defiance central to Harlock's world.