In the manga, Kai's personality is a proud and a very confident blader who is willing to sacrifice everything to get what he wants, which is through intense hard work and steel-hard determination, though he doesn't mind crushing people on the way up. His a quiet and a mysterious person. If he doesn't win at a thing he wants to he will feel down and when he comes back up even in a more ferocious determination to win. In the manga, a lot more is revealed of Kai's past. His father's name is Susumu Hiwatari, and little is seen of his mother.