Emperor Pilaf's long search for the powerful Black Star Dragon Balls, rumored to be twice as potent as Earth's usual ones, has finally come to an end. He plans to use their power to dominate the world, but Gokuu Son steps in and ruins his wish, resulting in Pilaf accidentally transforming Gokuu into a child. Consequently, the Black Star Dragon Balls are scattered across the galaxy, and Gokuu realizes that if they are not recovered within a year, Earth will be destroyed. To prevent this, he teams up with Trunks, a young adult, and his granddaughter, Pan, and embarks on a quest through the universe to retrieve the Black Star Dragon Balls and safeguard the prosperity of his planet.