Five years later, Goku is a young adult and father to Gohan, when Raditz arrives to Earth, and reveals to Goku that he is part of an alien race called the Saiyans who sent Goku with a mission to take over Earth for them before he suffered a head injury. Goku teams up with Piccolo to defeat Raditz but is also killed. Goku trains with King Kai in the afterlife, until he is revived to defeat Nappa and Vegeta, but Yamcha, Tenshinhan, Chaozu and Piccolo are killed. Krillin learns of other Dragon Balls on planet Namek and joins Bulma and Gohan to look for them to revive their friends and bring back Earth's Dragon Balls. The quest leads them to fights with the galactic tyrant Frieza's henchmen, the Ginyu Force, and Vegeta. In the battle with Frieza, Vegeta and Krillin are killed, and the fight ends when Goku transforms into the legendary Super Saiyan and defeats him.