Tea_Tae
Tea_Tae:It's a seance. She was only invited to talk to her son temporarily and then she'll have to leave as per the ritual's rules. It's true for all spirits who take part in a seance. And in Kanji's case it's not a seance but a possession. He is possessing Haejong' s body because Haejong allowed him to. Otherwise spirits can only possess people who have a weak mind and in most cases, they would be unwilling to leave.