Son Goku Jr. is the great-great-great-great-grandson of the legendary warrior Son Goku. However, unlike his predecessor he's not a brave fighter. He's constantly picked on by school bullies, his grandmother Pan sees this and she's worried, but even though Goku Jr. is not a strong and powerful Saiyan, he has a kind heart, and Pan loves him. When Pan gets sick Goku Jr. realizes he must do something if he doesn't want to lose Pan. Then he will remember about the legends of the Dragon Balls. It was told they granted a wish to the bearer, Goku Jr. needs a magical wish more than ever.
Ten years have passed since Goku left his friends and family to hone his skills. But Goku soon finds himself helpless against the mystical power of the Dragon Balls and an accidental wish made by the devious Emperor Pilaf. The wish; that Goku once again become a child! Goku, together with Trunks, and his own granddaughter Pan, blast off into the outer reaches of space in search of the mysterious Blackstar Dragon Balls. But these Dragon Balls have a fatal secret: if not collected within one year Earth will be destroyed.