So Kai's personality, 1 he's bipolar, because with that cause of desperation, Kai's brother eventually died, his brother had blue eyes was calm and a little cold, while Kai who only had red eyes was shy and not very social, with the death of his brother Kai was very traumatized, this trauma caused him to arouse the same feelings of his brother, making him bipolar, because of this he ended up getting heterochromia (The coloring of the eyes)