Jiora is a policeman from the planet Biretijon. One day, his ship crashes on Earth while he is pursuing dangerous criminals in space. He repairs the ship but, short of fuel, he has to stay on Earth and take the appearance of Chapat, a policeman from Slope Town he accidentally killed when landed on the planet. To raise the sum of 17 million yen needed to buy enough gold, which is used as a fuel for his ship, Jiora fights crime for money as Cashman, resuming his extraterrestrial appearance.

(Source: Dragonball Wiki)