Kei Yuki serves as the combat commander and navigator of the starship *Arcadia*, her strategic acumen honed by a life shaped by tragedy. Orphaned after Earth’s government neglected to prevent her parents’ deaths, she joined Captain Harlock’s crew following a daring rescue from a prison transport. Initially drawn to younger crewmate Tadashi Daiba through fleeting romantic feelings, their connection matured into unwavering camaraderie. Later narratives subtly imply unresolved affections toward Harlock himself, though these remain unspoken and undefined. A master of spacecraft piloting, tactical warfare, and radar operations, Kei also channels her artistry into playing the shamisen. Alternate continuities grant her an extraordinary navigational gift: the ability to chart flawless courses to any location she has visited. Her past harbors a brutal betrayal by fiancé Kazuya Katagiri, who orchestrated her father’s murder and colluded with alien invaders. This treachery solidified her allegiance to Harlock’s cause. In another timeline, she briefly captains the rogue crew *Flourite* until captured, possessed by a corrupting spirit, and freed only through external intervention that restored her mind. Stoic yet compassionate, Kei mediates crew disputes, mentors novices, and balances loyalty to Harlock with a willingness to dissent when principles demand. Later arcs reframe her as a protective figure, guiding the vulnerable through hostile worlds while confronting the stifling rigidity of terrestrial society. Recognizable by her blonde hair and signature pink jumpsuit adorned with a skull emblem, her appearance shifts across adaptations—cropped hair for practicality or disguises for covert ops. Her enduring narrative threads weave resilience through grief, fierce loyalty to chosen kin, and the struggle to reconcile duty with autonomy, whether defying tyrannical powers, alien incursions, or fractures within the *Arcadia*’s ranks.