 Goku leaves with Chi-Chi to keep his promise to marry her.Five years later, Goku is a young adult and father to a son, Gohan.A man named Raditz arrives on Earth, identifies Goku as his younger brother Kakarrot, and reveals to him that they are members of a nearly extinct extraterrestrial race called the , who sent Goku to conquer Earth for them; however, Goku had suffered a severe head injury as an infant and lost all memories of his mission.