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

(Source: Dragon Ball Wiki)