Before EXO’s debut, D.O. had actually left SM because of pressure from his parents. When SM was planning EXO, they went to D.O.’s house, in hopes of re-recruiting him. D.O. went back to SM just when Moonkyu left. Because of this, Kai, who was really close with Moonkyu, harbored ill feelings towards D.O. However, that is in the past; the two are on pretty good relations right now.