When vile aliens known as the Gamilons wreak nuclear havoc on Earth, a group of survivors refit the Japanese battleship Yamato for intergalactic travel and set off on a mission to retrieve a neutralizer that will eradicate the radiation from Earth's atmosphere.

Time to ease up ... not! Although the Yamato's crew has witnessed the end of the long, hard-fought Comet Empire War, a peaceful future will have to wait. While Dessler gathers together the shattered remnants of his Gamilus Empire, new forces are at work in the universe that could augur in another conflict. Seems the Black Star Empire has invaded Dessler's homeworld and is decimating it, all the while gathering power for its war machine.

The Yamato and her crew face the onslaught of the Comet Empire, a civilization from the Andromeda Galaxy who seek to conquer Earth, led by Prince Zordar. They have harnessed a comet and is using its terrible power to unleash destruction upon its rivals and inferiors... which are in fact everyone. The Space Battleship Yamato heads back into action. But this time, it shall not return, and much of the Yamato crew have signed on for their last voyage.