Jack and Kai were both taught by their grandfather, (who also taught Bobby Wasabi ). Unlike Jack, who cares about discipline and, honor, and respect, Kai is malicious, dishonorable and bitterly competitive. He defeated Jack so badly, Jack quit karate until he moved to Seaford. Since then, he and Jack don't get along and have a type of rivalry. He cheated the tournament when he let his friends injures Jack and decided to fight him but lost. He later came to Seaford and joined the Black Dragons because he heard they were Jack's archenemies.