Ding Xiao Yu (丁小雨) is an exchange student from "Kuo Nan High School" (拓南高中). He is one of the protagonists from the first series: KO One. He is the 4th ranked fighter on the KO Ranking Record, his fighting count being eight-thousand five-hundred, which later advances to over ten thousand. He is prone to giving others cold looks if they are not willing to leave him alone.