Outside of the prestigious Yatter Kingdom is a country of poverty. There, a young girl named Leopard learns that her mother, Dorothy, and her two close friends, Voltkatze and Elephantus, are direct descendants of the Doronbow Gang; Doronjo, Boyacky, and Tonzra, whose battle against the Yattermen long ago led to their people becoming exiled and living in poverty. Dorothy encourages Leopard to become a good girl and not become a villain like her ancestors. However, on the day of Leopard's ninth birthday, Dorothy develops an illness that cannot be treated with their country's medicine. Wanting to save her mother, Leopard goes with Voltkatze and Elephantus to try to get some help from the Yatter Kingdom, only to be attacked by the current Yattermen, who are shown to be cruel unlike their heroic ancestors, leaving them unable to prevent Dorothy from succumbing to her illness. Deciding the Yatterman are not the heroes she admired, Leopard takes on the name of Doronjo and forges a new Doronbow Gang with Voltkatze and Elephantus to get revenge on the Yatter Kingdom.