As Eishin Kuga—nicknamed "Mad Dog" for his unmistakable bloodlust—beats up his underlings, Yashiro watches and waits for his longtime friend to subdue him. Kanji Kageyama, an underground doctor, at last meets the young hothead whom Yashiro wants to recruit for his yakuza group. However, in light of Kuga's aversion toward Yashiro, Kageyama is ultimately left with the chore of temporarily housing him. But as Kageyama continues to insist that he has no interest in men, Kuga's shirtless presence, riotous attitude, and ceaseless teasing might just change his mind.

Earth has been conquered by the evil Illumidus Empire, with parallels drawn to the U.S. post World War II occupation of Japan. Captain Harlock with a group that will become his life long friends begin their fight against this tyranny visited upon the planet Earth, with no regard to the costs the struggle will have on them, caring only for the ideal of restoring freedom to the people of Earth.

In order to save a princess, Mantarou (Kid Muscle) and the gang must find a special ginseng. They are later joined by Kevin Mask.