Kei Yuki

A lady with an unknown age human woman with blonde hair who was already part of Harlock's crew at the time Tadashi came aboard, Kei was rescued by Harlock when he raided a ship that was transporting her as a prisoner back to Earth following an assault by her upon a military officer who had belittled her father's death. She initially seems to have a crush towards Tadashi Daiba, though the two eventually settle into a platonic friendship. In later additions to the franchise, she is instead portrayed as romantically inclined towards Harlock himself. She is the Arcadia's chief navigator and science officer, and she is the second-youngest crew member after Tadashi.

(Source: Wikipedia)