Kai has had a smoking problem before, coming back to it when he gets really stressed. It takes a lot for him to stop over and over again but still no one knows he does it.
Kai used to get no sleep as I kid after his parents left because he would work to make money and then stay up wanting his parents to come back. The only time he actually did sleep was when Nya couldn't so he had to fall asleep with her.
Kai uses fake confidence to cope. Otherwise he'd show everyone how much he actually hates himself. Everyone sees him as selfish, and even though he hates that title he'll keep it because he doesn't want to be titled as weak or pathetic.
He was hurting the most when Nya became one with the sea. No one would let him show it though because everyone was so worryed about Jay.
He doesn't have someone to go to when he gets scared, so he just stays up when he does. Since he'd older, he sees himself to have a label of strong so he can't let people see how weak and scared he is.
