Taking place five years after the events of the original Dragon Ball series, Kai covers the later stories of Son Goku, Earth's Greatest Warrior. Having finally settled down and made a family of his own, Goku seems to be adjusting well to the times of peace. However, the peace is short-lived as an intergalactic visitor claiming to be Goku's brother makes a crash landing to the planet. With the fate of entire galaxies at hand, Goku and the rest of the warriors must reunite, confronting progressively stronger foes in the continuous fight between good and evil.