The Succubus and her mom were caught. Her mom was caught earlier than her. Then the man was doing research about possessing Succubus. And Mom has been possessed by another man. After that man get used to the body of mom he possessed, he (or just say she) accompany with this man for his possession on this Succubus. Then this man just successfully possess the Succubus. And these guys just want to get their bodies because of the mana inside these bodies.