Kai has little background information due to the fact that she herself was born the way she looks now. Her creator Max has always been depressed over the loss of his first chobit, Chii. She was a model made machine that looked like a girl, but she had a expectancy to wear off. And when she did, Max decided to create a Chobit with a human heart. His younger brother Kai, had just past away, and he was allowed to use Kai's heart in order to create his newest chobit, who wouldn't die, named after his brother, Kai. Kai loved Max, from the bottom of her heart but she didn't want to be a rebound or a replacement for Chii. So she ran away heartbroken never to see Max again. Leaving Max desperate to find her.
