Did you know? 

Kai used to be quite crazy (in a bloodthirsty, monstrous way) as well, and Dog (Falte) didn't accept him - even hated him - for a long time. 

For the first few attempts at the series, Dog was forgiving toward his son and loved him as if nothing had ever happened. But I decided to make a twist, and in a couple of the stories, their relationship was rocky. Dog couldn't forgive Kai for being as monstrous and dangerous as he was, and Kai just wanted his father back.