Captain of the earth battleship Braves, Yamanaka was once in the position of trying to bring Harlock down, though his ship was no match for the Arcadia. In his heart, he envied Harlock's freedom, and when he learned that there was an alien presence upon earth, he and Harlock made an off-the-record agreement of sorts: to both counter the coming invasion, but not in any cooperative sense.

Yamanaka was forced to kill the wife of his chief engineer, Maji, when she was revealed as a Mazone assassin. Not understanding or caring, Maji nearly killed his superior officer, and left the service of the earth's space force to eventually join the Arcadia's crew. When a message (in a bottle, no less) apparently from a distressed Yamanaka is discovered, Maji is anxious for the opportunity to beg forgivness of his old friend, but they unfortunately arrive too late. As the message was bait in a Mazone ploy, Yamanaka's true fate is never known, only that he and his crew apparently went down fighting.

(Source: cornponeflicks.org/harlock/friends.html)