This is goku after the dragon ball saga. at this point he is on roshi island and out of no where this guy appears saying that his name is raditz and he is kakarot's aka goku's older brother and hes wondering why all the humans are still alive when goku was sent down years ago to eraticate the entire race. so raditz take gokus son gohan and flys off and waits for goku to show up to either join him or fight him. piccolo shows up just seconds after radiz left and him and goku fly off chaseing after radiz as fast as they could to get gohan back. they decide to work to gether to fight raditz.(will add more later)